tag:theconversation.com,2011:/au/topics/measurement-33991/articlesMeasurement – The Conversation2023-07-24T12:15:40Ztag:theconversation.com,2011:article/2046092023-07-24T12:15:40Z2023-07-24T12:15:40ZWill I ever need math? A mathematician explains how math is everywhere – from soap bubbles to Pixar movies<figure><img src="https://images.theconversation.com/files/533769/original/file-20230623-27-n6mym5.JPG?ixlib=rb-1.1.0&rect=0%2C3%2C2546%2C1810&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In addition to explaining natural phenomena, math can help strengthen your brain.</span> <span class="attribution"><span class="source">Liz Arnold</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=293&fit=crop&dpr=1 600w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=293&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=293&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=368&fit=crop&dpr=1 754w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=368&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/281719/original/file-20190628-76743-26slbc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=368&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em><a href="https://theconversation.com/us/topics/curious-kids-us-74795">Curious Kids</a> is a series for children of all ages. If you have a question you’d like an expert to answer, send it to <a href="mailto:curiouskidsus@theconversation.com">curiouskidsus@theconversation.com</a>.</em></p>
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<p><strong>Will I ever need math besides for school or work? – Hadassah G., age 9, New Jersey</strong></p>
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<p>It can be easy to think that you need math only to do your algebra or geometry homework or if you have a job as an engineer. But, in fact, math pops up everywhere – even in the soap bubbles in your kitchen sink. </p>
<p>While washing dishes when I was 13, I noticed that the soap bubbles formed tiny 3D polygons, packed together like a honeycomb, but not all of these shapes were perfectly round. Why did some of the bubbles look like hexagons? Why were others shaped like squares full of air? Why didn’t I see any star-shaped bubbles, or bubbles with spikes?</p>
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<a href="https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A tightly packed collection of hexagon-shaped, rainbow-colored bubbles against a dark background" src="https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532515/original/file-20230618-19-uiu174.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Math helps explain the shapes of bubbles and the reason they naturally pack together without any gaps.</span>
<span class="attribution"><span class="source">Adrienne Bresnahan/Moment via Getty Images</span></span>
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<p>When I learned that math could help answer these questions, I thought that was so cool! Now, as a professor of mathematics who <a href="https://scholar.google.com/citations?user=AcLUMzkAAAAJ&hl=en">studies how people learn math through play</a>, I understand why <a href="https://americanhistory.si.edu/collections/object-groups/geometric-models-minimal-surfaces-as-soap-films#:%7E:text=Brill%20in%201885.-,A%20minimal%20surface%20is%20the%20surface%20of%20smallest%20area%20of,is%20one%20of%20a%20series">bubbles are naturally lazy</a>. I even <a href="https://pubs.nctm.org/view/journals/mt/97/3/article-p165.xml">studied the math behind</a> the reason I saw only some shapes in soapy dishwater.</p>
<p>Besides helping explain the behavior of bubbles and other curiosities of nature, math is likely part of many of your everyday activities, along with the technology you enjoy and even the inner workings of your brain. Doing math isn’t just about computing, memorizing, solving an equation or doing word problems by yourself. It’s really about creative problem-solving and logical thinking with other people. </p>
<h2>Math in everyday life</h2>
<p>Many topics you learn in elementary school – like fractions, percentages and measurements – are useful in everyday life. </p>
<p>For example, if you want to build a fence around your house, <a href="https://www.instructables.com/How-to-Paint-a-Mural-of-Your-Favorite-Photo-The-Gr/">paint your walls a new color or with a design</a>, or <a href="https://www.youtube.com/watch?v=3TexumwK274">sew yourself a new outfit or quilt</a>, all of those activities require knowledge about measurement and scaling. More complicated construction projects, such as <a href="https://noticing.nysci.org/lesson/treehouse-design/">building a treehouse</a>, require lots of mathematical problem-solving skills.</p>
<p>Once you’ve laid out the plans for one of these projects, you need to buy all the materials. Percentages – which are special kinds of fractions – are especially important to understand when managing money. Understanding percentages can help you <a href="https://www.youtube.com/watch?v=iQK-3hLRXJA">budget your money</a> and <a href="https://www.youtube.com/watch?v=rP6Cg3ObMgQ&t=15s">increase your net worth</a>.</p>
<p>Beyond budgeting, you might find yourself using percentages when cooking a double batch of brownies, determining how much medicine to take when you’re sick or <a href="https://www.weatherstationadvisor.com/what-does-the-percentage-of-rain-mean/">understanding the weather forecast</a>.</p>
<h2>Your favorite technology needs math</h2>
<p>Math is an essential tool that animators use to make movies.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/Ei4wseRRJhc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Pixar artists use math to make movies like ‘Elemental.’</span></figcaption>
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<p><a href="https://www.theverge.com/2013/3/7/4074956/pixar-senior-scientist-derose-explains-how-math-makes-movies-games">Studios like Pixar</a> rely on <a href="https://www.slashfilm.com/531138/math-of-pixar/">ideas from geometry</a> to bring characters like Ember from “Elemental” to life. With an understanding of geometric transformations like reflections, rotations and translations, you can <a href="https://www.khanacademy.org/computing/pixar">use your computer</a> to make your own animations.</p>
<p>Coordinate systems, which are fundamental to geometry, show up in video games like Minecraft. The 2D Minecraft world uses a <a href="https://www.khanacademy.org/math/basic-geo/basic-geo-coord-plane">2D coordinate system</a> – with an x-axis and a y-axis – where you can move north, south, east or west. In the 3D Minecraft world, there’s also a z-axis, allowing you to move up and down. Middle and high school teachers can even <a href="https://education.minecraft.net/en-us/resources/math-subject-kit">use Minecraft</a> to help students learn math concepts.</p>
<p>Many high-paying jobs <a href="https://www.collegeconsensus.com/majors/highest-paying-careers-math-majors/">use math</a>, especially <a href="https://www.statology.org/probability-real-life-examples/">probability</a> – again, fractions. Understanding probability helps doctors identify how effective medical treatments are, informs coaches about <a href="https://www.youtube.com/watch?v=11fCMcEQkLo">ways their teams can improve</a> and aids <a href="https://www.youtube.com/watch?v=UiJiXNEm-Go">cryptographers</a> in keeping private information – like your email password or ATM PIN – secret. Cryptography combines probability with number theory to create <a href="https://www.giftofcuriosity.com/secret-codes-for-kids/">secret codes</a> that are difficult to crack.</p>
<h2>Math helps your brain</h2>
<p>Math can have a big impact on your internal life, too. You can use math activities to train your brain the same way you would train your body for a sport. Doing math helps your <a href="https://www.byjusfutureschool.com/blog/how-learning-math-can-benefit-your-childs-brain-in-incredible-ways/">brain become flexible</a> so you can better handle new tasks and ideas of all kinds. </p>
<p>Even doing things that don’t look like your math homework, such as crossword puzzles, word searches and board games like <a href="https://www.setgame.com/set/puzzle">Set</a> and <a href="https://shop.mattel.com/products/blokus-game-bjv44">Blokus</a>, are deeply mathematical activities that <a href="https://www.verywellmind.com/cognitive-training-long-term-improvement-2795014">help your brain get stronger</a>. This kind of mental training helps the brain pay attention and solve problems and improves memory. A strong working memory supports brain functions that lower the risk of <a href="https://doi.org/10.1016/j.trci.2017.09.002">Alzheimer’s disease and dementia</a>.</p>
<p>Having a stronger, more flexible brain also aids <a href="https://www.mathvalues.org/masterblog/what-is-quantitative-reasoning">quantitative literacy</a>, which can help you make sense of graphs that appear in the media, reflect critically about news and understand health and financial information. </p>
<p>Math can even help you <a href="https://www.wsj.com/articles/chatgpt-ai-math-po-shen-loh-1e9f80dc">outsmart artificial intelligence</a>. With the rise of AI, <a href="https://fortune.com/2023/05/06/what-jobs-will-rise-disappear-in-future-wef-artificial-intelligence/">it’s important</a> to be able to think creatively, reason logically and make connections between concepts – whether mathematical or not. Puzzling through a difficult math problem nurtures these skills, even if you don’t get the right answer right away. </p>
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<a href="https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&rect=84%2C92%2C2425%2C1708&q=45&auto=format&w=1000&fit=clip"><img alt="A woman leans across a table to help one of several young children building a cubical structure out of small colorful balls and sticks." src="https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&rect=84%2C92%2C2425%2C1708&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=439&fit=crop&dpr=1 600w, https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=439&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=439&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=551&fit=crop&dpr=1 754w, https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=551&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/533739/original/file-20230623-17-jq63y9.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=551&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Hortensia Soto demonstrates the hidden math of soap bubbles as part of Cafecito con Matemáticas, organized by Liz Arnold and Jocelyn Rios at Colorado State University.</span>
<span class="attribution"><span class="source">Liz Arnold</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
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<p>It’s important to remember that doing math doesn’t require you to be fast or to get the correct answer right away. In fact, you can learn a lot by <a href="https://www.waltonfamilyfoundation.org/stories/foundation/whats-a-great-way-to-learn-math-wrong-answers-only">getting the wrong answer</a>. Working with other people can also help you to make sure you really understand the problem and builds communication and <a href="https://mathsnoproblem.com/blog/teaching-practice/collaboration-for-meaningful-learning">teamwork skills</a>. </p>
<p>Math is so much more than memorizing times tables and filling out homework problem sets. So next time you kick back to watch your favorite animated movie, or start saving up for a fancy new tech gadget, hopefully you’ll appreciate how math is woven into so many parts of life.</p>
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<p class="fine-print"><em><span>Hortensia Soto does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Math is more than memorizing times tables and doing homework problems. It is woven into more aspects of your life than you might think.Hortensia Soto, Professor of Mathematics, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2036592023-07-03T12:06:01Z2023-07-03T12:06:01ZAncient Egyptians measured the first hour, and changed how we related to time<figure><img src="https://images.theconversation.com/files/529468/original/file-20230531-25771-bncig1.jpg?ixlib=rb-1.1.0&rect=0%2C15%2C2048%2C1174&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A detail from the astronomical ceiling at the Dendera temple in Egypt.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/manna4u/14826645968">(kairoinfo4u/flickr)</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>Humanity’s relationship with telling time began before the first written word, making it a challenge today to investigate the origin of many timekeeping units. </p>
<p>However, some time measurement units that derive from astronomical phenomena are quite easy to explain and likely were independently observed in many different cultures across the world. For example, measuring how long a day or a year is uses apparent motions of the sun relative to Earth, while measuring months comes from the phases of the moon.</p>
<p>Yet there are some measurements of time that do not have clear connections with any astronomical phenomena. </p>
<p>Two examples are the week and the hour. One of the most ancient written traditions, <a href="https://pcarlsberg.ku.dk/publishedtexts/">Egyptian hieroglyphic texts</a>, gives us new insight into the origin of the hour. It originated in the area of North Africa and the Middle East, and adopted in Europe before spreading around the world in the modern era.</p>
<h2>Time in Ancient Egypt</h2>
<p><a href="https://doi.org/10.2307/j.ctt14jxv34">The Pyramid Texts</a>, written before 2400 BCE, are the earliest writings from Ancient Egypt. Included in the texts is the word <em>wnwt</em> (approximately pronounced “wenut”), and the meaning-hieroglyph associated with it was a star. From this we gather that <em>wnwt</em> is associated with the night.</p>
<p>To understand the word <em>wnwt</em> and why it is now translated as “hour,” we go to the city of Asyut around 2000 BCE. There, the inside of wooden rectangular coffin lids are <a href="https://www.scientificamerican.com/article/decoding-the-star-charts-of-ancient-egypt/">sometimes decorated with an astronomical table</a>. </p>
<figure class="align-center ">
<img alt="astronomical procession on a temple ceiling" src="https://images.theconversation.com/files/534602/original/file-20230628-4980-4u2v1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/534602/original/file-20230628-4980-4u2v1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=321&fit=crop&dpr=1 600w, https://images.theconversation.com/files/534602/original/file-20230628-4980-4u2v1a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=321&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/534602/original/file-20230628-4980-4u2v1a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=321&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/534602/original/file-20230628-4980-4u2v1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=404&fit=crop&dpr=1 754w, https://images.theconversation.com/files/534602/original/file-20230628-4980-4u2v1a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=404&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/534602/original/file-20230628-4980-4u2v1a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=404&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Sopdet and Sahu (Sirius and Orion) shown in the left and right-hand boats, respectively, from the East Osiris Chapel on the roof of the temple in Dendera.</span>
<span class="attribution"><span class="source">(Sarah Symons)</span></span>
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<p>The table contains columns representing 10-day periods of the year; the Egyptian Civil Calendar had 12 months each having three 10-day “weeks,” all followed by five days of festivals. In each column, 12 star names are listed, making 12 rows. The whole table represents the changes in the star sky over the course of a whole year, similar to a modern star chart.</p>
<p>Those 12 stars are the earliest systematic division of the night into 12 time-areas, each governed by one star. However, the word <em>wnwt</em> never appears in association with these coffin star tables. </p>
<p>But around 1210 BCE in <a href="https://www.britannica.com/place/ancient-Egypt/The-New-Kingdom-c-1539-1075-bce">New Kingdom</a> — the period of ancient Egypt between the 16th and 11th centuries BCE — the link between the number of rows and the word <em>wnwt</em> is made explicit. </p>
<h2>Astronomical instructions</h2>
<p>One temple, <a href="https://openlibrary.org/books/OL13488676M/The_Osireion_at_Abydos">the Osireion at Abydos</a>, contains a wealth of astronomical information, including instructions on how to make a sundial and a text describing the motions of stars. It also contains a star table of the coffin type where, uniquely, the 12 rows are labelled with the word <em>wnwt</em>.</p>
<p>By the New Kingdom, there were 12 night-<em>wnwt</em> and also 12 day-<em>wnwt</em>, both clearly time measures. The idea of the hour is almost in its modern form but for two things. </p>
<p>First, although there are 12 day-hours and 12 night-hours, they are always expressed separately but not together as a 24-hour day. Day time was measured using shadows cast by the sun, while night hours were primarily measured by the stars. This could only be done while the sun and stars were visible, respectively, and there were two periods around sunrise and sunset that did not contain any hours. </p>
<p>Second, the New Kingdom <em>wnwt</em> and our modern hour differ in length. Sundials and water clocks demonstrate very clearly that the length of the <em>wnwt</em> varied throughout the year: long night hours around the winter solstice, long day hours around the summer solstice.</p>
<p>To answer the question of where the number 12 or 24 comes from, we have to find out why 12 stars were chosen per 10-day period. Surely, this choice is the true origin of the hour. Was 12 just a convenient number? Perhaps, but the origin of the coffin star tables suggests another possibility. </p>
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<a href="https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="ancient remains of an Egyptian temple in the desert" src="https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531361/original/file-20230612-206189-jorbr6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The Osireion temple in Abydos, Egypt provided a wealth of astronomical information.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
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<h2>Timekeeping stars</h2>
<p>The ancient Egyptians chose to use the bright star Sirius as a model, and selected other stars based on their behavioural similarity to Sirius. The key point seems to be that the timekeeping stars disappeared for 70 days each year, just like Sirius, even though the other stars were not as bright. The Osireion star text gives dates such that every 10 days, one Sirius-like star disappears and one star reappears, for the whole year.</p>
<p>Depending on the time of year, between 10 and 14 of these stars are visible each night. If recorded at 10-day intervals throughout the year, a table very much resembling the coffin star table emerges. By 2000 BCE, the table became more schematic than (in our sense) accurate, <a href="http://aea.physics.mcmaster.ca/">and a table with 12 rows had emerged</a>, resulting in the coffin tables we can see in museums in Egypt and elsewhere.</p>
<p>It is therefore possible that the choice of 12 as the number of hours of the night — and eventually 24 as the total number of hours from noon to noon — may be related to a choice of a 10-day week. </p>
<p>And so our modern hour originates from a confluence of decisions that happened more than 4,000 years ago.</p><img src="https://counter.theconversation.com/content/203659/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Cockcroft received funding from the Social Sciences and Humanities Research Council of Canada. </span></em></p><p class="fine-print"><em><span>Sarah Symons' research related to this article was funded by the Social Sciences and Humanities Research Council of Canada and the McMaster Arts Research Board.</span></em></p>Some time measurements, like months and years, use the movements of the moon and sun, respectively. But other time measurements, like the hour, aren’t clearly connected to astronomical phenomena.Robert Cockcroft, Assistant Professor, Physics and Astronomy, McMaster UniversitySarah Symons, Professor, Interdisciplinary Science, McMaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2030612023-04-18T04:57:04Z2023-04-18T04:57:04ZFrom platypus to parsecs and milliCrab: why do astronomers use such weird units?<figure><img src="https://images.theconversation.com/files/520396/original/file-20230412-22-m6601g.jpg?ixlib=rb-1.1.0&rect=0%2C308%2C2000%2C1356&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NASA / ESA / J. Hester / A. Loll</span></span></figcaption></figure><p>You may have heard about an asteroid set to fly near Earth that is <a href="https://www.jpost.com/science/article-735881">the size of 18 platypus</a>, or maybe the one that’s <a href="https://www.jpost.com/science/article-735473">the size of 33 armadillos</a>, or even one <a href="https://www.jpost.com/science/article-735299">the size of 22 tuna fish</a>. </p>
<p>These outlandish comparisons are the invention of Jerusalem Post journalist Aaron Reich (who <a href="https://twitter.com/aaronreich?lang=en">bills himself</a> as “creator of the <a href="https://www.jpost.com/science/article-708238">giraffe metric</a>”), but real astronomers sometimes measure celestial objects with units that are just as strange. </p>
<p>The idea of a planet that’s <a href="https://www.nature.com/articles/nature17448">85% the mass of Earth</a> seems straightforward. But what about a pulsar-wind nebula with a brightness of a few milliCrab? That’s where things get weird.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A top down image of a platypus swimming." src="https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518899/original/file-20230402-5213-uuxmaq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A platypus that is approximately 1/18th of the size of Asteroid 2023 FH7.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Platypus#/media/File:Platypus.jpg">Stefan Kraft / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Why do astronomers use such strange units?</h2>
<p>The basic problem is that lots of things in space are way too big for our familiar units. </p>
<p>Take my whippet Astro, who is 94cm long. Earth’s radius is about 638 million cm, or 7.5 million Astros. </p>
<p>Jupiter’s radius is 11.2 Earths, or 85 million Astros. That number of Astros is a bit ridiculous, which is why we adjust our unit choice to one that makes more sense. </p>
<figure class="align-center ">
<img alt="A white whippet with a brown splotch over his eye is lying down in the grass with a blue sky with puffy clouds in the background. He's staring off into the distance." src="https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518897/original/file-20230402-18-fg5ndr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Astro the whippet contemplating the wonders of the Universe (probably).</span>
<span class="attribution"><span class="source">Laura Driessen</span></span>
</figcaption>
</figure>
<p>At an even larger scale, consider the star Betelguese: its radius is 83,000 Earths, or 764 times the radius of the Sun. So if we want to talk about how big Betelgeuse is, it’s much more convenient to use the radius of the Sun as our unit, instead of the radius of Earth (or to describe it as 632 billion Astros).</p>
<h2>Heavy stuff</h2>
<p>If we want to measure how heavy an asteroid is, we could <a href="https://www.jpost.com/science/article-733651">do it with camels</a> – but in space we’re more interested in mass than in weight. Mass is a measure of how much stuff something is made of. </p>
<p>On Earth the weight of an object, like Astro, depends on the mass of Astro and the gravitational force pulling him down to the ground. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-mass-49299">Explainer: what is mass?</a>
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</em>
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<hr>
<p>We can think of weight in terms of how hard it is to lift an 18kg Astro off the ground. This would be easy to do on Earth, even easier somewhere with lower gravity like the Moon, and much harder somewhere with higher gravity like Jupiter. </p>
<p>On the other hand, Astro’s mass is how much stuff he’s made of – and it’s the same no matter which planet he’s on. </p>
<p>Astronomers use Earth and the Sun as handy units to measure mass. For example, the Andromeda galaxy is approximately <a href="https://arxiv.org/abs/2211.15928">three trillion times</a> the mass of the Sun (or 3×10<sup>41</sup> – that’s a 3 followed by 41 zeros – Astros).</p>
<h2>Astronomical units and parsecs</h2>
<p>Astronomers also use comparisons to measure how far apart things are. The Sun and Earth are 149 million kilometres apart, and we give this distance a name: an astronomical unit (AU). </p>
<p>For an even twistier unit of distance, we use the parsec (insert Han Solo <a href="https://starwars.fandom.com/wiki/Kessel_Run">Kessel run</a> joke here). Parsec is short for “parallax second”, and if you remember your trigonometry, this is the length of the hypotenuse of a right-angle triangle when the angle is 1 arcsecond (1/3,600 degrees) and the “opposite” side of the triangle is 1 AU. </p>
<p>Parsecs are handy for measuring even bigger distances because 1 parsec = 206,265 AU. For example, the centre of our very own galaxy, the Milky Way, is about 8,000 parsecs away from Earth, or 1.6 million AU.</p>
<h2>Magnitudes</h2>
<p>If we want to measure how bright something is, astronomical units of measurement get even weirder. In the second century BC, the ancient Greek astronomer Hipparchus looked up at space and gave the brightest stars a value of 1 and the faintest stars a value of 6. </p>
<p>Notice here that a brighter star has a lower number. We call these brightness values “magnitudes”. The Sun has an apparent magnitude of –26! </p>
<figure class="align-center ">
<img alt="A image of the Sun as an orange ball with dark spots and bright loops." src="https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518900/original/file-20230402-28-zgz3aj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">An image of the Sun taken by NASA’s Solar Dynamics Observatory.</span>
<span class="attribution"><span class="source">NASA/SDO</span></span>
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</figure>
<p>Even more confusing than a negative brightness, each single step in magnitude is a 2.512 times difference in brightness. The star Vega has an apparent magnitude of 0, which is two and a bit times brighter than the star Antares with an apparent magnitude of 1.</p>
<h2>At last, the milliCrab</h2>
<p>The light we see with our eyes is, for obvious reasons, called “visible” light. The light we use to take pictures of your bones is called X-ray light. </p>
<p>When astronomers use X-ray light to observe the sky we sometimes measure brightness in “Crabs”. </p>
<p>The Crab is a rapidly spinning neutron star (or pulsar) in the remains of an exploded star that is extremely bright when we look at it using our X-ray telescopes. It’s so bright in X-ray light that astronomers have been using it to <a href="https://ui.adsabs.harvard.edu/abs/2005SPIE.5898...22K/abstract">calibrate their telescopes</a> since the 1970s. </p>
<figure class="align-center ">
<img alt="A bright, multi-coloured supernova remnant with dusty, wispy filaments and something resembling a tornado (the pulsar wind nebula) in the centre." src="https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=474&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=474&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=474&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=596&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=596&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518898/original/file-20230402-4247-w4mh75.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=596&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Image of the Crab Nebula where red is radio from the Very Large Array, yellow is infra-red from the Spitzer Space Telescope, green is visible from the Hubble Space Telescope, and blue and purple are X-ray from the XMM-Newton and Chandra X-ray Observatories respectively.</span>
<span class="attribution"><span class="source">NASA, ESA, G. Dubner (IAFE, CONICET-University of Buenos Aires) et al.; A. Loll et al.; T. Temim et al.; F. Seward et al.; VLA/NRAO/AUI/NSF; Chandra/CXC; Spitzer/JPL-Caltech; XMM-Newton/ESA; and Hubble/STScI</span></span>
</figcaption>
</figure>
<p>So every X-ray astronomer knows how bright a Crab is. And if we’re talking about a particular object, say a <a href="https://ui.adsabs.harvard.edu/abs/2019ApJ...885...48G/abstract">black hole binary system called GX339-4</a>, and it’s only five thousandths as bright as the Crab, we say it’s 5 milliCrab bright.</p>
<p>But buyer beware! The brightness of the Crab is different depending on what energy of X-ray light you’re looking at, and it also <a href="https://ui.adsabs.harvard.edu/abs/2011ApJ...727L..40W/abstract">changes over time</a>.</p>
<p>Whether we use lions or tigers or Crabs, astronomers make sure to define the units we’re using. There’s no use using an armadillo, or even your local whippet, unless you’ve made sure the definition is clear.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/beating-heart-of-the-crab-nebula-62282">Beating heart of the Crab Nebula</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/203061/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Laura Nicole Driessen is part of MeerTRAP, which is supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No 694745).</span></em></p>An asteroid ‘the size of 33 armadillos’ might be a flight of fancy, but real astronomers measure celestial objects with units that are just as strange.Laura Nicole Driessen, Postdoctoral researcher in radio astronomy, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1864882022-08-18T15:10:12Z2022-08-18T15:10:12ZBeyond GDP: changing how we measure progress is key to tackling a world in crisis – three leading experts<p>It’s an odd quirk of history that, on the first day of his ill-fated presidential campaign in March 1968, Robert F Kennedy chose to talk to his audience about the <a href="https://cusp.ac.uk/themes/aetw/rfk-gdp50/">limitations of gross domestic product</a>* (GDP) – the world’s headline indicator of economic progress.</p>
<p>It seems stranger still that, despite the power of that iconic speech, growth in <a href="https://www.imf.org/external/pubs/ft/fandd/basics/gdp.htm">GDP</a> remains to this day the predominant measure of progress across the world. Economic success is measured by it. Government policy is assessed by it. Political survival hangs on it.</p>
<p>Kennedy’s speech inspired a host of critiques. It has been quoted by presidents, prime ministers and Nobel laureates. <a href="https://press.princeton.edu/books/paperback/9780691169859/gdp">Yet GDP itself has survived until now</a>, more-or-less unscathed. But amid ever-louder concerns about the failure of national economies to tackle the multiple threats posed by climate change, spiralling energy costs, insecure employment and widening levels of inequality, the need to define and measure progress in a different way now looks as unarguable as it is urgent.</p>
<h2>The goods, the bads, and the missing</h2>
<p>In simple terms, GDP is a measure of the size of a country’s economy: how much is produced, how much is earned, and how much is spent on goods and services across the nation. The monetary total, whether in dollars or euros, yuan or yen, is then adjusted for any general increase in prices to give a measure of “real” economic growth over time. When governments adopt policies to pursue economic growth, this is how those policies are evaluated.</p>
<p>Since 1953, GDP has been the headline measure in a complex <a href="https://unstats.un.org/unsd/nationalaccount/sna.asp#:%7E:text=The%20System%20of%20National%20Accounts%20(SNA)&text=The%20SNA%20describes%20a%20coherent,definitions%2C%20classifications%20and%20accounting%20rules.">system of national accounts</a> overseen by the United Nations. Developed during the second world war, these accounts were motivated in part by the need to determine how much governments could afford to spend on the war effort.</p>
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<img alt="" src="https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/288776/original/file-20190820-170910-8bv1s7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><strong><em>This story is part of Conversation Insights</em></strong>
<br><em>The Insights team generates <a href="https://theconversation.com/uk/topics/insights-series-71218">long-form journalism</a> and is working with academics from different backgrounds who have been engaged in projects to tackle societal and scientific challenges.</em></p>
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<p>But in measuring the monetary value of economic activity, GDP can incorporate many of the “bads” that detract from our quality of life. War, pollution, crime, <a href="https://theconversation.com/is-prostitution-really-worth-5-7-billion-a-year-33497">prostitution</a>, traffic congestion, disasters like wildfires and the destruction of nature – all can have a positive impact on GDP. Yet they cannot really be construed as components of economic success.</p>
<p>At the same time, there are numerous aspects of our lives that simply go missing from this conventional account. The inequality in our societies. The contributions from unpaid work. The labour of those who care for the young and the elderly at home or in the community. The depletion of natural resources or biodiversity. And the value of data and many digital services.</p>
<p>What lies outside the market, including public services funded out of taxation, remains unmeasured in a metric of monetary exchange. Kennedy was blunt: “[GDP] measures everything, in short, except that which makes life worthwhile.”</p>
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<p>It’s a sentiment that has resonance half a century later. In a striking encounter during the Brexit debate, a UK academic was trying to convey to a public meeting the dangers of leaving the EU. The impact on GDP would dwarf any savings from the UK’s contributions to the EU budget, he told the audience. “That’s your bloody GDP!” <a href="https://www.theguardian.com/commentisfree/2017/jan/10/blunt-heckler-economists-failing-us-booming-britain-gdp-london">shouted</a> a woman in the crowd. “It’s not ours.”</p>
<p>This sense of an indicator out of touch with reality may be one of the reasons there is momentum for reform. When GDP conceals crucial differences between the richest and the poorest in society, it inevitably says little about the prospects for ordinary people.</p>
<p>But there are other reasons too for an emerging change of heart. The pursuit of GDP growth as a policy goal, and the impact that has on government, business and personal decision-making, has accompanied increasing devastation of the natural world, a loss of forests and habitats, the destabilisation of the climate, and near-meltdowns of the world’s financial markets. At the same time, GDP has become a poor measure of the technological transformation of society.</p>
<p>Its tenacity as a measure of progress, despite these well-known limitations, arises from factors which are on the one hand technocratic, and on the other sociological. As the headline measure in a sophisticated system of national accounts, GDP has a technocratic convenience and analytical elegance that remains unsurpassed by many alternative measures. Its authority arises from its ability to be simultaneously a measure of production output, consumption expenditure and income in the economy.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/gdp-numbers-are-not-what-they-seem-how-they-boost-us-and-uk-at-expense-of-developing-countries-162468">GDP numbers are not what they seem: how they boost US and UK at expense of developing countries</a>
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<p>Despite this complex framework, it also offers the deceptive simplicity of a single headline figure which appears to be directly comparable from year to year and across nations, based on the simple (if inadequate) idea that more economic activity necessarily leads to a better life.</p>
<p>However, the combined technical authority and political usefulness of this idea has led to “path dependence” and forms of social lock-in that are difficult to address without significant effort. Think of switching to an alternative as being like switching from driving on the left to the right-hand side of the road.</p>
<p>Yet what we measure matters. And while we’re busy looking in the wrong direction, as Kennedy pointed out, bad things can happen. Kennedy’s campaign – and his critique of GDP – was cut cruelly short on June 5 1968, when he was fatally wounded by an assassin’s bullet. More than half a century later, his call for reform of how we assess progress (or its absence) has never been stronger.</p>
<h2>The trouble with GDP: historical flaws</h2>
<p>The way societies have understood and measured progress has changed considerably over the centuries. Measurement of “the economy” as a whole is a relatively modern, 20th-century concept, beginning with efforts by statisticians and economists such as Colin Clark and Simon Kuznets in the 1920s and 1930s to understand the impact of financial crisis and depression.</p>
<p>Kuznets, now best known for his <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/environmental-kuznets-curve">curve</a> describing the relationship between GDP and income inequality, was particularly concerned to develop a measure of economic welfare rather than just activity. For example, he argued for omitting expenditures that were unwelcome necessities rather than services or goods consumers actively wanted – such as defence spending.</p>
<p>However, the second world war overtook and absorbed these earlier notions of a single measure of economic welfare, resulting in what first became modern gross national product <a href="https://apps.bea.gov/scb/2021/03-march/pdf/0321-reprint-gnp.pdf">(GNP</a>), and then GDP. The imperative – set out on the Allied side by John Maynard Keynes in his 1940 pamphlet <a href="https://fraser.stlouisfed.org/title/pay-war-6021">How to Pay for the War</a> – was measuring productive capacity, and the reduction in consumption required to have enough resources to support the military effort. Economic welfare was a peacetime concern.</p>
<p>Post-war, unsurprisingly, American and British economists such as Milton Gilbert, James Meade and Richard Stone took the lead in codifying these statistical definitions through the UN – and its process for agreeing and formalising definitions in the system of national accounts (SNA) is still in place today. However, since at least the 1940s, some important inadequacies of both the SNA and GDP have been widely known and debated.</p>
<p>Indeed, as long ago as 1934, Margaret Reid published her book <a href="https://www.journals.uchicago.edu/doi/10.1086/255033">Economics of Household Production</a>, which pointed out the need to include unpaid work in the home when thinking about economically useful activity.</p>
<p>The question of whether and how to measure the household and informal sectors was debated during the 1950s – particularly as this makes up a larger share of activity in low-income countries – but was omitted until some countries, including the UK, started to create <a href="https://www.ons.gov.uk/economy/nationalaccounts/satelliteaccounts/compendium/householdsatelliteaccounts/previousReleases">household satellite accounts</a> around 2000. Omitting unpaid work meant, for instance, that the UK’s increased productivity growth between the 1960s and 1980s was then overstated, because it in part reflected the <a href="https://voxeu.org/article/changing-business-cycles-role-women-s-employment">inclusion of many more women in paid work</a> whose contributions had previously been invisible to the national GDP metric.</p>
<p>Another longstanding and widely understood failure of GDP is not including environmental externalities and the depletion of natural capital. The metric takes incomplete account of many activities that do not have market prices, and ignores the additional social costs of pollution, greenhouse gas emissions and similar outputs associated with economic activities.</p>
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Read more:
<a href="https://theconversation.com/an-obsession-with-economic-growth-will-not-make-the-best-use-of-natural-assets-30283">An obsession with economic growth will not make the best use of natural assets</a>
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<p>What’s more, the depletion or loss of assets such as natural resources (or indeed buildings and infrastructure lost in disasters) boosts GDP in the short term because these resources are used in economic activities, or because there is a surge in construction after a disaster. Yet the long-term opportunity costs are never counted. This massive shortcoming was widely discussed at the time of landmark publications such as the <a href="https://www.clubofrome.org/publication/the-limits-to-growth/">1972 Limits to Growth report</a> from the Club of Rome, and the 1987 <a href="https://www.are.admin.ch/are/en/home/media/publications/sustainable-development/brundtland-report.html">Brundtland Report</a> from the World Commission on Environment and Development.</p>
<p>As with household and informal activity, there has been recent progress in accounting for nature, with the development of the <a href="https://seea.un.org/content/about-seea">System of Environmental Economic Accounting</a> (SEEA) and publication of regular (but separate) statistics on natural capital in a number of countries. The <a href="https://www.ons.gov.uk/economy/environmentalaccounts/methodologies/naturalcapital">UK</a> has again been a pioneer in this area, while the <a href="https://www.whitehouse.gov/ostp/news-updates/2022/04/24/accounting-for-nature-on-earth-day-2022/">US recently announced</a> it would start following this approach too.</p>
<h2>New challenges to the value of GDP</h2>
<p>Other, perhaps less obvious failings of GDP have become more prominent recently. Digitisation of the economy has transformed the way many people spend their days in work and leisure, and the way many businesses operate, yet these transformations are not apparent in official statistics.</p>
<p>Measuring innovation has always been tricky, because new goods or improved quality need to be incorporated into observable prices and quantities – and what is the metric for a unit of software or management consultancy? But it is harder now because many digital services are “free” at point of use, or have the features of public goods in that many people can use them at the same time, or are intangible. For example, data is without doubt improving the productivity of companies that know how to use it to improve their services and produce goods more effectively – but how should a dataset’s value, or potential value, to society (as opposed to a big tech company) be estimated?</p>
<p><a href="https://www.insee.fr/en/statistiques/4770156?sommaire=4770271">Recent work</a> looking at the price of telecommunications services in the UK has estimated that output growth in this sector since 2010 has ranged anywhere from <a href="https://www.ons.gov.uk/economy/nationalaccounts/uksectoraccounts/methodologies/doubledeflationmethodsanddeflatorimprovementstouknationalaccountsbluebook2021">about 0% to 90%</a>, depending on how the price index used to convert market prices to real (inflation-adjusted) prices takes account of the economic value of our rapidly growing use of data. Similarly, it is not obvious how to incorporate advertising-funded “free” search, crypto currencies and <a href="https://theconversation.com/nfts-explained-what-they-are-why-rock-stars-are-using-them-and-why-theyre-selling-for-millions-of-dollars-156389#:%7E:text=NFTs%20are%20digital%20certificates%20that,alternative%20to%20a%20central%20database.">NFTs</a> in the measurement framework.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Crowd looking into art showroom" src="https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479625/original/file-20220817-8075-ynmg73.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Street artist Banksy’s temporary showroom critiquing global society in south London, October 2019.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/london-uk-october-2-2019-crowds-1523572547">Shutterstock</a></span>
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</figure>
<p>A key limitation of GDP, particularly in terms of its use as an indicator of social progress, is that it offers no systematic account of the distribution of incomes. It is entirely possible for average or aggregate GDP to be rising, even as a significant proportion of the population find themselves worse off.</p>
<p>Ordinary incomes have stagnated or fallen in recent decades even as the richest in society have become wealthier. In the US, for example, <a href="https://www.nytimes.com/interactive/2017/08/07/opinion/leonhardt-income-inequality.html">Thomas Piketty and his colleagues</a> have shown that in the period between 1980 and 2016, the top 0.001% of society saw their incomes grow by an average of 6% per year. Income for the poorest 5% of society fell in real terms.</p>
<p>Given these many issues, it might seem surprising that the debate about “<a href="https://www.bennettinstitute.cam.ac.uk/blog/beyond-gdp-impact/">Beyond GDP</a>” is only now – possibly – turning into actions to change the official statistical framework. But paradoxically, one hurdle has been the proliferation of alternative progress metrics.</p>
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Read more:
<a href="https://theconversation.com/how-poorer-citizens-pay-the-price-of-economic-change-in-the-uk-172356">How poorer citizens pay the price of economic change in the UK</a>
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<p>Whether these are single indices that combine a number of different indicators or dashboards showcasing a wide range of metrics, they have been ad hoc and too varied to build consensus around a new global way of measuring progress. Few of them provide an economic framework for consideration of trade-offs between the separate indicators, or guidance as to how to interpret indicators moving in different directions. There is a breadth of information but as a call to action, this cannot compete against the clarity of a single GDP statistic.</p>
<p>Statistical measurement is like a technical standard such as voltage in electricity networks or the Highway Code’s rules of the road: a shared standard or definition is essential. While an overwhelming majority might agree on the need to go beyond GDP, there also needs to be enough agreement about what “beyond” actually involves before meaningful progress on how we measure progress can be made.</p>
<h2>Change behaviour, not just what we measure</h2>
<p>There are many <a href="https://theconversation.com/uk/search?adapter=pg3&date=all&language=en&page=2&q=beyond+GDP&sort=relevancy">visions to supplant GDP growth</a> as the dominant definition of progress and better lives. In the wake of the COVID pandemic, it has been reported that most people want a <a href="https://theconversation.com/life-after-covid-most-people-dont-want-a-return-to-normal-they-want-a-fairer-more-sustainable-future-173290">fairer, more sustainable future</a>.</p>
<p>Politicians can make it sound straightforward. Writing in 2009, the then-French president Nicolas Sarkozy explained he had convened a commission – led by internationally acclaimed economists Amartya Sen, Joseph Stiglitz and Jean-Paul Fitoussi – on the measurement of economic performance and social progress on the basis of a firm belief: that we will not change our behaviour “unless we change the ways we measure our economic performance”.</p>
<p>Sarkozy also committed to encouraging other countries and international organisations to follow the example of France in implementing <a href="https://ec.europa.eu/eurostat/documents/8131721/8131772/Stiglitz-Sen-Fitoussi-Commission-report.pdf">his commission’s recommendations</a> for a suite of measures beyond GDP. The ambition was no less than the construction of a new global economic, social and environmental order.</p>
<p>In 2010, the recently-elected UK prime minister, David Cameron, launched a programme to implement the Sarkozy commission’s recommendations in the UK. He described this as starting to measure progress as a country “not just by how our economy is growing, but by how our lives are improving – not just by our standard of living, but by our quality of life”.</p>
<p>Once again, the emphasis was on measurement (how far have we got?) rather than behaviour change (what should people do differently?). The implication is that changing what we measure necessarily leads to different behaviours – but the relationship is not that simple. Measures and measurers exist in political and social spheres, not as absolute facts and neutral agents to be accepted by all.</p>
<p>This should not dissuade statisticians from developing new measures, but it should prompt them to engage with all who might be affected – not just those in public policy, commerce or industry. The point after all is to change behaviour, not just to change the measures.</p>
<p>Economists are increasingly adopting complex systems thinking, including both social and psychological understandings of human behaviour. For example, <a href="https://www.economist.com/letters/2017/09/14/letters-to-the-editor">Jonathan Michie</a> has pointed to ethical and cultural values, as well as public policy and the market economy, as the big influences on behaviour. <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3548365">Katharina Lima di Miranda and Dennis Snower</a> have highlighted social solidarity, individual agency and concern for the environment alongside the “traditional” economic incentives captured by GDP.</p>
<h2>GDP alternatives in practice</h2>
<p>Since Kennedy’s 1968 critique, there have been numerous initiatives to replace, augment or complement GDP over the years. Many dozens of indicators have been devised and implemented at local, national and international scales.</p>
<p>Some aim to account more directly for subjective wellbeing, for example by measuring self-reported life satisfaction or “happiness”. Some hope to reflect more accurately the state of our natural or social assets by developing adjusted monetary and non-monetary measures of “<a href="https://www.worldbank.org/en/news/press-release/2021/10/27/global-wealth-has-grown-but-at-the-expense-of-future-prosperity-world-bank">inclusive wealth</a>” (including a team at the University of Cambridge led by this article’s co-author Diane Coyle). The UK government has accepted this as a meaningful approach to measurement in several recent policy documents, including its <a href="https://www.gov.uk/government/publications/levelling-up-the-united-kingdom">Levelling Up white paper</a>.</p>
<p>There are two fundamental arguments for a wealth-based approach:</p>
<ul>
<li><p>It embeds consideration for sustainability in the valuing of all assets: their value today depends on the entire future flow of services they make available. This is exactly why stockmarket prices can fall or rise suddenly, when expectations about the future change. Similarly, the prices at which assets such as natural resources or the climate are valued are not just market prices; the true “accounting prices” include social costs and externalities.</p></li>
<li><p>It also introduces several dimensions of progress, and flags up the correlations between them. Inclusive wealth includes produced, natural and human capital, and also intangible and social or organisational capital. Using a comprehensive wealth balance sheet to inform decisions could contribute to making better use of resources – for example, by considering the close links between sustaining natural assets and the social and human capital context of people living in areas where those assets are under threat.</p></li>
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<p>Other initiatives aim to capture the multi-dimensional nature of social progress by compiling a dashboard of indicators – often measured in non-monetary terms – each of which attempts to track some aspect of what matters to society.</p>
<p>New Zealand’s <a href="https://www.treasury.govt.nz/information-and-services/nz-economy/higher-living-standards/our-living-standards-framework">Living Standards Framework</a> is the best-known example of this dashboard approach. Dating back to a 1988 Royal Commission on Social Policy and developed over more than a decade within the New Zealand Treasury, this framework was precipitated by the need to do something about the discrepancy between what GDP can reflect and the ultimate aim of the Treasury: to make life better for people in New Zealand.</p>
<p>The NZ Treasury now uses it to allocate fiscal budgets in a manner consistent with the identified needs of the country in relation to social and environmental progress. The relevance to combating climate change is particularly clear: if government spending and investment are focused on narrow measures of economic output, there is every possibility that the deep decarbonisation needed to achieve a just transition to a <a href="https://theconversation.com/uk/topics/net-zero-carbon-economy-102230">net zero carbon economy</a> will be impossible. Equally, by identifying areas of society with declining wellbeing, such as children’s mental health, it becomes possible to allocate Treasury resources directly to alleviate the problem.</p>
<p>The <a href="https://www.ons.gov.uk/peoplepopulationandcommunity/wellbeing/articles/measuringnationalwellbeing/apr2017">UK’s Measuring National Wellbeing</a> (MNW) programme, directed by Paul Allin (a co-author of this article), was launched in November 2010 as part of a government-led drive to place greater emphasis on wellbeing in national life and business. Much of the emphasis was on the subjective <a href="https://www.ons.gov.uk/peoplepopulationandcommunity/wellbeing/bulletins/measuringnationalwellbeing/april2020tomarch2021">personal wellbeing measures</a> that the UK’s Office for National Statistics (ONS) continues to collect and publish, and which appear to be increasingly taken up as policy goals (driven in part by the <a href="https://whatworkswellbeing.org/">What Works Centre for Wellbeing</a>).</p>
<p>The MNW team was also charged with addressing the full “beyond GDP” agenda, and undertook a large consultation and engagement exercise to find out what matters to people in the UK. This provided the basis for a <a href="https://www.ons.gov.uk/peoplepopulationandcommunity/wellbeing/articles/measuringnationalwellbeing/internationalcomparisons2019">set of indicators</a> covering ten broad areas which are updated by the ONS from time to time. While these indicators <a href="https://www.ons.gov.uk/releases/qualityoflifeintheukaugust2022">continue to be published</a>, there is no evidence that they are being used to supplement GDP as the UK’s measure of progress.</p>
<p>Accounting for inequality within a single aggregate index is obviously tricky. But several solutions to this problem exist. One of them, advocated by the Sen-Stiglitz-Fitoussi commission, is to report median rather than mean (or average) values when calculating GDP per head.</p>
<p>Another fascinating possibility is to adjust the aggregate measure using a welfare-based index of inequality, such as the one devised by the late Tony Atkinson. An exercise using the <a href="https://www.census.gov/topics/income-poverty/income-inequality/about/metrics/atkinson-index.html">Atkinson index</a> carried out by Tim Jackson, also a co-author of this article, calculated that the <a href="https://limits2growth.org.uk/publication/aetw_no2/">welfare loss associated with inequality</a> in the UK in 2016 amounted to almost £240 billion – around twice the annual budget of the NHS at that time.</p>
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Read more:
<a href="https://theconversation.com/the-search-for-an-alternative-to-gdp-to-measure-a-nations-progress-the-new-zealand-experience-118169">The search for an alternative to GDP to measure a nation's progress – the New Zealand experience</a>
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<p>Among the most ambitious attempts to create a single alternative to GDP is a measure which has become known as the <a href="https://oxfordre.com/environmentalscience/view/10.1093/acrefore/9780199389414.001.0001/acrefore-9780199389414-e-776">Genuine Progress Indicator</a> (GPI). Proposed initially by economist Herman Daly and theologian John Cobb, GPI attempts to adjust GDP for a range of factors – environmental, social and financial – which are not sufficiently well reflected in GDP itself.</p>
<p>GPI has been used as a progress indicator in the US state of Maryland since 2015. Indeed, a <a href="https://www.congress.gov/bill/117th-congress/house-bill/4894?r=5&s=1">bill introduced to US Congress in July 2021</a> would, if enacted, require the Department of Commerce to publish a US GPI, and to “use both the indicator and GDP for budgetary reporting and economic forecasting”. GPI is also used in <a href="http://www.gpiatlantic.org/">Atlantic Canada</a>, where the process of building and publishing the index forms part of this community’s approach to its development.</p>
<h2>A potential gamechanger?</h2>
<p>In 2021, the UN secretary-general António Guterres concluded his Our Common Agenda <a href="https://www.un.org/en/content/common-agenda-report/assets/pdf/Common_Agenda_Report_English.pdf">report</a> with a call for action. “We must urgently find measures of progress that complement GDP, as we were tasked to do by 2030 in target 17.19 of the <a href="https://sdgs.un.org/2030agenda">Sustainable Development Goals</a>.” He repeated this demand in his <a href="https://www.un.org/sg/en/content/sg/speeches/2022-01-21/remarks-general-assembly-his-priorities-for-2022">priorities for 2022</a> speech to the UN General Assembly.</p>
<p>Guterres called for a process “to bring together member states, international financial institutions and statistical, science and policy experts to identify a complement or complements to GDP that will measure inclusive and sustainable growth and prosperity, building on the work of the Statistical Commission”.</p>
<p>The first manual explaining the UN’s system of national accounts was published in 1953. It has since been through five revisions (the last in 2008) designed to catch up with developments in the economy and financial markets, as well as to meet user needs across the world for a wider spread of information.</p>
<p><a href="https://unstats.un.org/unsd/nationalaccount/Towards2025.asp">The next SNA revision</a> is currently in development, led by the UN Statistics Division and mainly involving national statistical offices, <a href="https://www.escoe.ac.uk/programmes/national-accounts-and-beyond-gdp/">other statistical experts</a> and institutional stakeholders such as the IMF, World Bank and Eurostat.</p>
<p>But unlike the UN’s COP processes relating to climate change and, to a lesser extent, biodiversity, there has, to date, been little wider engagement with interested parties – from business leaders and political parties to civil society, non-governmental organisations and the general public.</p>
<p>As the British science writer <a href="https://www.bbc.co.uk/sounds/play/m000ynb8">Ehsan Masood</a> has observed, this revision process is happening below the radar of most people who are not currently users of national accounts. And this means many very useful ideas that could be being fed in are going unheard by those who will ultimately make decisions about how nations measure their progress in the future.</p>
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Read more:
<a href="https://theconversation.com/why-uks-treasured-free-market-economy-will-not-achieve-net-zero-180922">Why UK's 'treasured free-market economy' will not achieve net zero</a>
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<p>The essence of sustainable development was captured in the 1987 <a href="https://www.un.org/esa/sustdev/csd/csd15/media/backgrounder_brundtland.pdf">Brundtland Report</a>: “To contribute to the welfare and wellbeing of the current generation, without compromising the potential of future generations for a better quality of life.” Yet it remains unclear how the next SNA revision will provide such an intergenerational lens, despite a new focus on “missing” capitals including natural capital.</p>
<p>Similarly, while the revision programme is addressing globalisation issues, these are only about global production and trade – not, for example, the impacts of national economies on the environment and wellbeing of other countries and populations.</p>
<p>Ambitious deadlines have been set further into the future: achieving the UN’s Sustainable Development Goals by 2030, and reducing global net emissions of greenhouse gases to zero before 2050. The SNA revision process – which will see a new system of national accounts agreed in 2023 and enacted from 2025 – is a key step in achieving these longer-term goals. That is why opening up this revision process to wider debate and scrutiny is so important.</p>
<h2>It’s time to abandon this ‘GDP fetish’</h2>
<p>One lesson to learn from the history of indicators, such as those about poverty and social exclusion, is that their impact and effectiveness depends not only on their technical robustness and their fitness for purpose, but also on the political and social context – what are the needs of the time, and the prevailing climate of ideas?</p>
<p>The current SNA revision should be a process as much about the use and usefulness of new measures as about their methodological rigour. Indeed, we might go as far as <a href="https://www.ft.com/content/e3b356b4-dbcc-42ef-811d-74d649139916">Gus O’Donnell</a>, the former UK cabinet secretary, who said in 2020: “Of course measurement is hard. But roughly measuring the right concepts is a better way to make policy choices than using more precise measures of the wrong concepts.”</p>
<p>In short, there is an inherent tension involved in constructing an alternative to GDP – namely achieving a balance between technical robustness and social resonance. The complexity of a dashboard of indicators such as New Zealand’s Living Standards Framework is both an advantage in terms of meaningfulness, and a disadvantage in terms of communicability. In contrast, the simplicity of a single measure of progress such as the Genuine Progress Indicator – or, indeed, GDP – is both an advantage in terms of communication, and a disadvantage in terms of its inability to provide a more nuanced picture of progress.</p>
<p>Ultimately, a plurality of indicators is probably essential in navigating a pathway towards a sustainable prosperity that takes full account of individual and societal wellbeing. Having a wider range of measures should allow for more diverse narratives of progress.</p>
<p>Some momentum in the current SNA revisions process and ongoing statistical research is directed toward measurement of inclusive wealth – building on the economics of sustainability brought together in <a href="https://www.gov.uk/government/publications/final-report-the-economics-of-biodiversity-the-dasgupta-review">Partha Dasgupta’s recent review of the economics of biodiversity</a>. This framework can probably gain a broad consensus among economists and statisticians, and is already being implemented by the UN, starting with natural capital and environmental accounting.</p>
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<em>
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Read more:
<a href="https://theconversation.com/nature-how-do-you-put-a-price-on-something-that-has-infinite-worth-154704">Nature: how do you put a price on something that has infinite worth?</a>
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<p>Including wellbeing measures in the mix would signal that wellbeing matters, at least to some of us, while also recognising that many different things can affect wellbeing. The evidence to date is that planting wellbeing measures in a different part of the data ecosystem means they will be overlooked or ignored. Wellbeing measures are not a panacea, but without them we will continue to do things that restrict rather than enhance wellbeing and fail to recognise the potential economic, social and environmental benefits that a wellbeing focus should bring.</p>
<p>The task of updating the statistical framework to measure economic progress better is non-trivial. The development of the SNA and its spread to many countries took years or even decades. New data collection methodologies should be able to speed things up now – but the first step in getting political buy-in to a better framework for the measurement of progress is an agreement about what to move to.</p>
<p>National accounting needs what the name suggests: an internally-consistent, exhaustive and mutually exclusive set of definitions and classifications. A new framework will require collecting different source data, and therefore changing the processes embedded in national statistical offices. It will need to incorporate recent changes in the economy due to digitalisation, as well as the long-standing issues such as inadequate measurement of environmental change.</p>
<figure class="align-center ">
<img alt="Politician surrounded by children in a street" src="https://images.theconversation.com/files/479656/original/file-20220817-1692-564oum.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/479656/original/file-20220817-1692-564oum.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/479656/original/file-20220817-1692-564oum.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/479656/original/file-20220817-1692-564oum.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/479656/original/file-20220817-1692-564oum.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/479656/original/file-20220817-1692-564oum.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/479656/original/file-20220817-1692-564oum.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">‘That which makes life worthwhile’: Robert Kennedy visits a summer reading programme in Harlem, 1963.</span>
<span class="attribution"><a class="source" href="https://www.alamy.com/stock-photo-attorney-general-robert-kennedy-surrounded-by-african-american-children-50061032.html?imageid=DDD82FF2-5A5A-4E7C-82DC-5E56884212EA&p=167342&pn=1&searchId=0c74a3c5497b7d923e9264b334f535ea&searchtype=0">Alamy</a></span>
</figcaption>
</figure>
<p>Ultimately, this “beyond GDP” process needs to grapple not only with measurement problems but also with the various uses and abuses to which GDP has been put. Kennedy’s neat summary that it measures “everything except that which makes life worthwhile” points as much to the misuse of GDP as to its statistical limitations. Its elegance in being simultaneously a measure of income, spending and output means that in some form, it is likely to remain a valid tool for macroeconomic analysis. But its use as an unequivocal arbiter of social progress was never appropriate, and probably never will be.</p>
<p>Clearly, the desire to know if society is moving in the right direction remains a legitimate and important goal – perhaps more so now than ever. But in their search for a reliable guide towards social wellbeing, governments, businesses, statisticians, climate scientists and all other interested parties must abandon once and for all what the Nobel Laureate Stiglitz called a “GDP fetish”, and work with civil society, the media and the public to establish a more effective framework for measuring progress.</p>
<p><em>*Strictly speaking, Robert Kennedy referred to gross national product (GNP) in his 1968 speech. You can read more about the UN’s Towards the 2025 SNA process <a href="https://unstats.un.org/unsd/nationalaccount/towards2025.asp">here</a>.</em></p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=112&fit=crop&dpr=1 600w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=112&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=112&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=140&fit=crop&dpr=1 754w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=140&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/313478/original/file-20200204-41481-1n8vco4.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=140&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption"></span>
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<p class="fine-print"><em><span>Paul Allin is a member of the UK National Statistician's Expert User Advisory Committee and he is the Royal Statistical Society's Honorary Officer for National Statistics. Views expressed in this article are personal do not necessarily represent those of the NSEUAC or the RSS.. </span></em></p><p class="fine-print"><em><span>Diane Coyle receives funding from the Economic Statistics Centre of Excellence and ESRC via the Productivity Institute. She is a member of the UK National Statistician's Expert User Advisory Committee and of the Royal Statistical Society. These are personal views. </span></em></p><p class="fine-print"><em><span>Tim Jackson is Director of the Centre for the Understanding of Sustainable Prosperity which receives funding from the Economic and Social Research Council and Laudes Foundation. CUSP provides the secretariat for the All-Party Parliamentary Group on Limits to Growth. The views expressed here are personal.</span></em></p>Amid the global threats posed by climate change, spiralling energy costs, insecure employment and widening inequality, the need to rethink our notion of progress is now an urgent priority.Paul Allin, Visiting Professor in Statistics, Imperial College LondonDiane Coyle, Professor of Public Policy, University of CambridgeTim Jackson, Professor of Sustainable Development and Director of the Centre for the Understanding of Sustainable Prosperity (CUSP), University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1756282022-01-27T13:30:43Z2022-01-27T13:30:43ZHow is snowfall measured? A meteorologist explains how volunteers tally up winter storms<figure><img src="https://images.theconversation.com/files/442790/original/file-20220126-19-155hewg.jpg?ixlib=rb-1.1.0&rect=377%2C238%2C1719%2C1257&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Strict rules guide the official count for how much solid precipitation fell.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/man-with-siege-at-winter-royalty-free-image/133440630"> Photos by Vesuviante/Moment via Getty Images</a></span></figcaption></figure><p>The Blue Hill Observatory, a few miles south of Boston, recorded the deepest snow cover in its 130-year history, an incredible 46 inches, in February 2015. The same month, Bangor, Maine, tied its record for deepest snow at 53 inches. Mountainous locations will sometimes see triple-digit snow depths. </p>
<p>Impressive numbers, for sure, but assuming you have a measuring stick long enough to reach the ground beneath all the white, how hard can it be to measure? You stick a ruler or yardstick into the snow and get a number, right? Well, not so fast. It’s a little <a href="https://doi.org/10.1080/00431670009605830">more complicated</a> than you might think to get those oh-so-important snow totals for winter storms.</p>
<p>Since 1890, the U.S. National Weather Service has relied on a network of volunteer observers, all strictly adhering to the <a href="http://www.nws.noaa.gov/om/coop/reference/Snow_Measurement_Guidelines.pdf">NWS guidelines</a>, to come up with snow measurement numbers over a region. There are over <a href="https://www.weather.gov/coop/Overview">8,700 cooperative observers</a> <a href="https://www.weather.gov/coop/">across the country</a> who send in their weather data to the NWS daily, some who have done it for over <a href="https://www.weather.gov/gjt/coop_observers">75 years</a>!</p>
<p>Snow measurement is inherently inexact, but attending to one’s surroundings and sticking to the guidelines help those of us who do it on a regular basis stay consistent – and with long-term weather records, consistency is arguably just as important as accuracy.</p>
<p>First, you need to understand the difference between snow depth and snowfall.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="man leans on ruler poking into snow-covered ground" src="https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The author measuring the paltry snow accumulation at his observation location in Pennsylvania. Note the instrument shelters in the background.</span>
<span class="attribution"><span class="source">Marisa Ferger</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>How is snow depth measured?</h2>
<p>Snow depth should be a measure of the average depth in a given location and its immediate surroundings. It’s usually rounded to the nearest whole number. To get a representative number, you need a site with minimal drifting (not always easy to find), and several measurements should be averaged to get a final number. I like 10 because it makes the math easy.</p>
<p>Careful measurement is vital in order to make reasonable estimates for the amount of liquid contained in the snowpack. As hard as it is to believe at times, the snow will eventually melt, and rapid melting could cause problems with flooding. Also, hydrologists’ models that are <a href="https://theconversation.com/climate-change-will-mean-more-multiyear-snow-droughts-in-the-west-121406">used to predict water levels</a> critically depend upon good initial data collection, though improved satellite data has helped reduce their reliance on any individual measurement.</p>
<p>Snow depth is like the sum of individual snowfalls, if one assumes no <a href="http://water.usgs.gov/edu/watercyclesublimation.html">sublimation</a> – <a href="https://theconversation.com/snow-can-disappear-straight-into-the-atmosphere-in-hot-dry-weather-162910">snow turning into water vapor</a> – or melting from the first snowfall until now. That assumption would almost always be wrong, of course. But if you suspend reality for a moment, the depth will still never exceed the sum of all snowfalls because snow is compressible. So, two 10.5-inch (27-centimeter) snowfalls may accumulate to a depth of only 17 inches (43 cm).</p>
<p>It’s the compressibility of snow that causes the greatest consternation with snowfall measurement.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="square white board with measuring stick lying across it on the ground" src="https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">National Weather Service snow board and snow measuring stick.</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:2013-10-14_12_27_14_National_Weather_Service_snow_board_and_snow_measuring_stick.JPG">Famartin/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>How are snowfall totals measured?</h2>
<p>Snowfall is the amount of snow that accumulates during a given time, usually a 24-hour period. In a perfect world, this 24-hour period would end at midnight, but the vast majority of National Weather Service cooperative observers take their daily observation in the morning. </p>
<p>To properly measure snowfall, you need a flat, level surface. As with snow depth, you want to avoid areas of drifting when you’re measuring snowfall. The National Weather Service <a href="https://www.weather.gov/dvn/snowmeasure">suggests the use of a snow board</a>, which is a white surface that will absorb very little sunlight and stay close to the ambient air temperature. Any cold surface will do, though.</p>
<p>Keeping in mind that consistency is critical, the goal here is to make an accurate measurement that is representative of the surrounding area and consistent with others making snowfall measurements.</p>
<h2>More complicated cases of measurement</h2>
<p>So, let’s consider three common scenarios. Here in the eastern U.S., we often have to deal with snow that changes to rain during the course of a storm. Imagine 6.0 inches (15 cm) of snow falls, then an inch (2.5 cm) of sleet which compacts the snow to a 4-inch (10-cm) depth. Then, on top of that falls an inch of freezing rain which further compacts the snow to 2.6-inch (6.6-cm) depth by the end of the observation period. What should be listed as the daily snowfall? The snow depth?</p>
<p>In this situation, when the snow transitions to sleet, the snow board should be cleared and the maximum depth of snow recorded – 6 inches (15 cm) in this case. Do the same with the sleet and this will add an inch (2.5 cm) to the snowfall – technically, “solid precipitation” – total. Freezing rain is never added to the daily snowfall total because it is in liquid form when it reaches the ground. Thus, the daily snowfall is 7.0 inches (measured to the nearest tenth of an inch) (17.8 cm), while the snow depth at observation is rounded up from 2.6 inches (6.6 cm) to 3 inches (7.6 cm).</p>
<p>Imagine a case where three heavy snow showers occur one afternoon, two dumping 1.5 inches (3.8 cm) before melting completely and then a third 1.8-inch (4.6-cm) event. The daily snowfall would be reported as the greatest depth achieved during that period, 1.8 inches (4.6 cm). This assumes an observer is there to measure each short-lived accumulation. But because most observers are volunteers, that’s not always the case, unfortunately.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="snowy suburban street scene" src="https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Looks like a lot of snow – but how to quantify that?</span>
<span class="attribution"><a class="source" href="http://pixabay.com/en/snowy-street-deep-snow-winter-554957/">JillWellington</a></span>
</figcaption>
</figure>
<p>Finally, we come to the controversy. Let’s assume a steady snow falls for the entire 24-hour period at a rate of 2.0 inches (5.1 cm) per hour. If the snow board were cleared every hour, the daily snowfall would be 48.0 inches (122 cm).</p>
<p>But what if the observer could be there only at the daily observation time? By then the snow will have compacted some, depending upon the temperature and the amount of liquid in the snow, which can vary between about a quarter-inch and 3 inches (0.6 - 7.6 cm) of liquid water for every 10 inches (25 cm) of snow. That liquid-to-solid ratio depends upon many factors, including the temperature within the cloud where the snow was produced, which in turn helps determine how large the snowflakes can get. Large, airy snowflakes produce less-dense snow and lower liquid-to-solid ratios, in general.</p>
<p>[<em>Like what you’ve read? Want more?</em> <a href="https://memberservices.theconversation.com/newsletters/?source=inline-likethis">Sign up for The Conversation’s daily newsletter</a>.]</p>
<p>This once-a-day observer would log significantly less snowfall – for the exact same event – than the person who cleared the board every hour. This is a problem. The National Weather Service addresses it by mandating that no more than four snowfall measurements should be made in any 24-hour period. Ideally, then, an observer who went to the snowboard every six hours and cleared 10.5 inches (26 cm), 9.3 inches (23.5 cm), 11.5 inches (29 cm) and 10.8 inches (27 cm) would get the officially correct snowfall measurement of 42.1 inches (107 cm). </p>
<p>Several years ago, an observer in New York measured 77.0 inches (196 cm) of snow in a 24-hour period, which would have broken the record for heaviest one-day snowfall in U.S. history. However, the <a href="http://www.weatheranswer.com/public/tughill.pdf">National Weather Service determined</a> that he cleared the snowboard much too frequently, thus inflating the daily total and invalidating the record.</p>
<p>Intrigue, suspense, mystery, controversy. So much more than just sticking a ruler in the snow. If it all sounds like a daily dose of meteorological fun to you, maybe you’ve got what it takes to volunteer for the NWS’ <a href="http://www.nws.noaa.gov/om/coop/index.htm">Cooperative Observer</a> program, where it’s not all about the white stuff. Daily high and low temperatures and precipitation of all forms are also measured, to strict NWS standards, of course.</p>
<p>For those who want to stick with measuring only what falls from the sky, check out the <a href="https://cocorahs.org">Community Collaborative Rain, Hail and Snow Network</a>. Anyone may join, but those who live “in the middle of nowhere” can provide an invaluable service by helping fill gaps in the data that limit the effectiveness of hydrological models.</p>
<p><em>This is an updated version of <a href="https://theconversation.com/where-do-those-snowfall-totals-on-the-news-come-from-37686">an article originally published</a> on Feb. 19, 2015.</em></p><img src="https://counter.theconversation.com/content/175628/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bill Syrett does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s hard to get accurate measurements, but a nationwide network of more than 8,000 volunteers with rulers and specific standards reports after every storm.Bill Syrett, Associate Teaching Professor of Meteorology and Atmospheric Science and Manager of the Joel N. Myers Weather Center, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1682132021-09-21T16:14:00Z2021-09-21T16:14:00ZReturn of imperial system on cards for Brexit Britain – measurements have always been political<p>Last year, the return of <a href="https://www.express.co.uk/news/uk/1297212/blue-passport-how-to-get-blue-brexit-passport">blue passports</a> was touted as a symbol of Britain taking back control following Brexit. Some in government would now like to see Britain’s imperial measurements <a href="https://www.bbc.co.uk/news/uk-politics-58597693">make a comeback.</a> As part of a review on EU laws still in place after Brexit, the government plans to remove a ban on selling goods using only imperial units.</p>
<p>The collective memory of many eurosceptics is that the metric system was imposed by Europe in the 1970s upon an <a href="https://www.journals.uchicago.edu/doi/10.1086/710308">unwilling British public</a>. There was political turmoil over quotidian tasks – buying milk and beer in litres rather than in pints. Metric measurements made European integration seem very real, close to home and <a href="https://ehsthelongrun.net/2017/04/11/inching-towards-the-meter-britain-europe-and-the-politics-of-economic-integration/">highly undesirable</a> to some.</p>
<p>A succession of European directives on measurements crystallised and maintained the sceptical view that Brussels was forcing even the Queen to <a href="https://www.telegraph.co.uk/news/uknews/1337979/Queen-obeys-Europe-and-adopts-metric-rule.html">obey European laws</a>. Politicians pointed to Brussels compulsorily replacing pints and inches with <a href="https://youtu.be/XHuKq22yXH4">litres and metres</a> as evidence that joining Europe meant a loss of British identity.</p>
<p>In fact, metrication was not imposed on Britain after joining the EEC in 1975. British industrialists lobbied politicians to commit to a programme on metrication in the 1960s. The commitment to metrication and <a href="https://www.itv.com/news/anglia/2021-02-15/when-there-were-240-pennies-in-a-pound-and-a-pint-of-beer-cost-15p">currency decimalisation</a> precedes Britain’s entry into the European Common Market. But measurement systems have long been used as convenient tools and symbols for political ends.</p>
<p>The English state had unsuccessfully attempted to introduce standardised measurements at least since the Magna Carta of 1225. Indeed, the traditional imperial measurements in the form we recognise today only date to 1824, with the passage of the Weights and Measures Act. </p>
<p>A select committee of the British parliament in 1758 sought to remove the “despotic influence” of tradition from the British measurement system. But successive legislative reforms of Britain’s measurements in 19th century <a href="https://www.cambridge.org/core/books/markets-and-measurements-in-nineteenthcentury-britain/85F0EA3E89FC1A4B89E6089E362B25A1#fndtn-information">consistently rejected</a> the decimal metric system.</p>
<p>Ironically, since 1960 all measurement systems worldwide – including the British and US imperial systems – are calibrated to the <a href="https://www.bipm.org/en/measurement-units">Système International d'Unités (SI)</a> which in turn are based on the historical metric system devised in France during the 1790s.</p>
<h2>Revolution, colonialism and socialism</h2>
<p>Throughout much of history, measurement units were based on the human body or everyday objects – a “foot”, “basket” or “cup”. Nationalised measurement systems – a relatively modern phenomenon – arose with the need for effective tax collection mechanisms and came with increased government control.</p>
<p>Reforms to measurement systems were frequently framed in the language of nation-building. In 1790, Thomas Jefferson argued that (North) American measurements were based on systems brought by the first settlers from England. Jefferson convinced Congress to adopt a decimal currency, but firmly advised retaining the English (imperial) units. The US thus was one of the first nations with a decimal currency, but still fiercely resists using the decimal metric measurements.</p>
<p>The metric system was one of the enduring legacies of the French Revolution and a product of the scientific Enlightenment that swept <a href="https://www.bbc.com/travel/article/20180923-how-france-created-the-metric-system">France</a> in the 18th century. The French demanded “one law, one weight, one measure” on the eve of revolution. But when they were made to use the new metric system in 1793, they resolutely rejected it. </p>
<p>Parisian shoppers were suspicious of the unfamiliar system and thought it gave shopkeepers an unfair advantage. Shopkeepers, who thought otherwise, took to illegally keeping two sets of weights and measures, the <a href="https://en.wikipedia.org/wiki/Units_of_measurement_in_France_before_the_French_Revolution#/media/File:Pernes_-_Mesures_anciennes.JPG">old and the new</a>. Even government officials hated using the new, unfamiliar units. Widespread hostility to the new metric system led Napoleon to retract it. Metric measurements were first used in Belgium and the Netherlands before the French began using them in 1840.</p>
<p>Colonial rule often led to profound changes to measurement systems in other parts of the world. The British replaced <a href="http://www.dozenalsociety.org.uk/history/indian.html">Indian measurement systems</a> with imperial measurements, asserting its colonial authority. During India’s independence struggle, Jawaharlal Nehru argued that the decimal metric measurements were part of ancient Hindu tradition of using decimal arithmetic and thus not “foreign”. India adopted metric measurements in 1956 and rejected the imperial units which were seen as obsolete and <a href="https://pastandpresent.org.uk/looking-back-to-the-future-nationalist-visions-of-india-in-the-twentieth-century">reminders of colonialism</a>.</p>
<p>Socialism, like colonialism, was also a powerful driver of measurement change. In China, multiple measurement systems coexisted relatively peacefully during the <a href="https://muse.jhu.edu/article/766798">Qing period</a> (1644-1912). But this became problematic during the the Republic of China era (1911-1949) when the multiple systems of measurement generated intolerable confusion in daily life. </p>
<p>The People’s Republic introduced the metric system soon after it was established in 1949. The situation stabilised only after 1985, once the political turmoil of the Cultural Revolution ended. In Russia, the Bolsheviks discarded the <a href="https://static1.squarespace.com/static/5275adb7e4b0298e6ac6bc86/t/55c8a3f7e4b026cbe91d35bc/1439212535440/4.4gordin.pdf">old Tsarist system</a> and made metric measurements the “progressive foundation” of the world’s first socialist state. </p>
<h2>Measurements and upheaval</h2>
<p>Changes to measurement systems have historically disrupted finely balanced social relationships and traditional ways of life. At times, this has created an uncertain economic future for the local communities. No wonder ordinary people often protested against such changes.</p>
<p>During the <a href="https://read.dukeupress.edu/hahr/article/57/3/401/150218/The-Brazilian-Peasantry-Reexamined-The">Quebra Quilos Revolt</a> of 1874 in Brazil, rioting peasants smashed the newly introduced metric kilogram weights in local markets. They destroyed property and measuring instruments and beat up shopkeepers. Hence the name of the revolt, which translates to “smash the kilos”.</p>
<p>English people have also protested against compulsory introduction of imperial measurements by the government. When the authorities imposed the unfamiliar Winchester bushel in Gloucestershire, Somerset and Wiltshire, angry mobs rioted against any imposition of imperial standards between 1670 and 1800. So much for the imagined popular <a href="https://www.theweek.co.uk/news/uk-news/954167/boris-johnson-revive-imperial-measurements">“tolerance of traditional imperial measures”</a> by those currently ruling the country.</p>
<p>Yet for all this resistance, history teaches us that people across different cultures and times have always coped – even prospered – with changes to measurement systems.</p><img src="https://counter.theconversation.com/content/168213/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Aashish Velkar does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A look at the many systems of measurement that have been lost and changed throughout history.Aashish Velkar, Senior Lecturer in Economic History, University of ManchesterLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1177132019-07-28T12:30:51Z2019-07-28T12:30:51ZRedefining the kilogram means redefining how we measure wealth<figure><img src="https://images.theconversation.com/files/277236/original/file-20190530-69063-16j0i2o.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5183%2C3444&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In May 2019, the measure of a kilogram was changed. This has implications for how we measure wealth.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Between November 2008 and October 2014, an additional $85 billion was created on an almost-monthly basis by the United States Federal Reserve Bank. As a result, <a href="https://money.cnn.com/2018/07/31/investing/stocks-market-federal-reserve-qe/index.html">the total amount of newly created electronic cash</a> used to purchase government bonds in that period is estimated to be $4.5 trillion. </p>
<p>On World Metrology Day 2019, <a href="https://futurism.com/the-byte/redefined-kilogram">the kilogram was fundamentally redefined</a>. It has now become a number whose value is defined by <a href="https://www.vox.com/science-and-health/2018/11/14/18072368/kilogram-kibble-redefine-weight-science">the energetics of a hoard of photons</a>. Accordingly, those same electromagnetic phenomena that created $4.5 trillion in electronic cash are also now controlling our traditional understanding of wealth itself.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284117/original/file-20190715-173329-1i4ifxp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Martin J.T. Milton, the head of the International Bureau of Weights and Measures, holds a replica of the International Prototype Kilogram in Sèvres, near Paris, in October 2018.</span>
<span class="attribution"><span class="source">Christophe Ena/AP Photo</span></span>
</figcaption>
</figure>
<p>I have been teaching and writing about coherent systems of units and their importance for accurate characterization of heat and mass transfer processes in food-processing operations. My work also examines the effective utilization of units in the trading and processing of agricultural commodities. For example, conversions between mass and volume dictate <a href="https://www.agric.gov.ab.ca/app19/calc/crop/bushel2tonne.jsp">price returns</a> and <a href="https://www.canada.ca/en/health-canada/services/understanding-food-labels/serving-size.html">nutrient content</a> in many sectors of our food supply chains.</p>
<h2>Gold standards</h2>
<p>Up until 1931, the value of a British pound was defined by its ability to be exchanged for 0.235849 ounces of gold. Likewise, until 1971, a U.S. dollar was valued at 0.028571 ounces of gold. To some economists, the U.S. government’s decision to abandon the <a href="https://doi.org/10.1177%2F0032329218823648">gold standard</a> was licence for the dollar to claim values divorced from traditional measures of wealth. </p>
<p>Freed from the obligation to redeem a given number of dollars against a specific mass of an immutable metal, the Federal Reserve was able to tweak currency flows to hit its desired liquidity targets. The outcome of six years of <a href="https://doi.org/10.1111/j.1468-0297.2012.02551.x">quantitative easing</a> was a global economy that landed softly from the financial crisis of 2008, but at the price of a <a href="https://doi.org/10.1080/13563467.2015.1041478">greater concentration of wealth for those already wealthy</a>.</p>
<p>The change in the kilogram that occurred on May 20th, 2019, eliminated another long-held standard, which will also have global ramifications: <a href="https://doi.org/10.1088/1681-7575/ab0013">a redefinition of the very mass of gold</a>.</p>
<h2>Standard purpose</h2>
<p>The need for fixed and legitimate standards has been a longstanding trade issue. Some 2,800 years ago, <a href="https://www.bible.com/bible/100/AMO.8.5.NASB">Amos decried the prevalence of shrunken bushels and inflated shekels in the trading of cereals</a> in Jerusalem.</p>
<p>But it was in post-revolutionary France where <a href="https://archive.org/details/lesystmemtri00bigo/page/n10">measurement standards were defined for trading on a global scale</a>. When the new government devised the metre as the standard for length, it was conceived as a fraction of the Earth’s circumference. In defining a unit for mass, the kilogram was assigned as the mass of water contained within a volume governed by that standard of length.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=875&fit=crop&dpr=1 600w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=875&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=875&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1099&fit=crop&dpr=1 754w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1099&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/284131/original/file-20190715-173355-uulya4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1099&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One of six temporary prototypes made in 1793 by the French Temporary Commission on Weights and Measures. Originally called the ‘grave,’ the name was changed to ‘kilogram’ in 1795. The prototype is in the collection of the U.S. National Institute of Standards and Technology Museum in Bethesda, Md.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Grave_kilogram_standard_1793.jpg">U.S. National Institute of Standards and Technology Museum</a></span>
</figcaption>
</figure>
<p>To ensure that all traders adhered to these new standards of length and mass, prototypes of the metre and the kilogram were fabricated - the first, ironically enough, by the former king’s royal jeweller. These prototypes were made of precious metal, not because of its value, but because of its inertness. </p>
<p>They were retained under lock and key, but were periodically available for standardization and correction of more widely available secondary standards of length and mass. Although new physical versions of the prototype metre and kilogram were produced in 1889, these physical standards endured because no better standards were available. As a result, the physical kilogram lasted for more than 200 years.</p>
<h2>Scientific standards</h2>
<p>With advances in science, additional standards were appended to the kilogram and metre. We now have <a href="https://doi.org/10.1088/0026-1394/31/6/011">seven standards</a> from which everything that we know about our universe is defined and quantified. This includes how many pecks of wheat we get for a pound of gold. Yes, I did write pecks and pounds. Despite our southern neighbour’s stolid indifference to Canada’s metrication, their standard for mass, a physical pound, was eliminated as early as 1893.</p>
<p>Just as new measurement technologies brought <a href="https://www.history.com/this-day-in-history/galileo-is-convicted-of-heresy">Galileo into conflict with accepted cosmological standards</a>, advanced techniques revealed deficiencies in the standards in use. So in 1960, <a href="https://doi.org/10.1139/p61-088">the prototype metre was abandoned</a>. </p>
<p>If size did matter, it was measured against standards regulated by the properties of light, specifically a defined number of wavelengths of an orange line emitted when the noble gas krypton was electrically excited. The prototype metre thus became a quaint historical artefact.</p>
<p>The <a href="https://doi.org/10.1088/1681-7575/ab0013">prototype kilogram</a> was then left as the only tangible standard of the scientific and social upheaval that flowed from the ideas of Thomas Jefferson, John Adams and Benjamin Franklin.</p>
<p>As we advance well into the 21st century, the lifetime of this <a href="https://www.bipm.org/en/measurement-units/faqs.html">one remaining tangible standard has just expired</a>.</p>
<p>It was recognized for a number of years that gentle polishing and environmental pollution had been incrementally <a href="https://doi.org/10.1088%2F0026-1394%2F33%2F6%2F1">changing the mass of the prototype kilogram</a>. The simple solution of replacing the old prototype kilogram with a new one is no longer tenable in an age of enlightenment where the ideas of <a href="https://doi-org.uml.idm.oclc.org/10.1098/rspb.1967.0069">John Dalton</a>, <a href="https://doi.org/10.1007/s00016-002-8363-7">Max Planck</a> and <a href="https://plato.stanford.edu/entries/statphys-Boltzmann/">Ludwig Boltzmann</a> dictate a new fiat.</p>
<p>In the future, <a href="https://doi.org/10.1088%2F1681-7575%2Faa966c">mass will no longer be mass</a> as tangibly defined throughout history. A select group with access to sophisticated equipment will tweak the number that now defines mass as they see fit, or “<a href="https://www.nytimes.com/2018/11/16/science/kilogram-physics-measurement.html">conjure [it] on demand</a>.”</p>
<p>From this point onwards, it matters not what <a href="https://doi.org/10.1111/johs.12139">mass of Franklin D Roosevelt’s confiscated gold</a> exists in Fort Knox; the same electrons that create the Federal Reserve’s wealth now govern our very definition of the gold’s existence.</p>
<p>[ <em><a href="https://theconversation.com/ca/newsletters?utm_source=TCCA&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=expertise">Expertise in your inbox. Sign up for The Conversation’s newsletter and get a digest of academic takes on today’s news, every day.</a></em> ]</p><img src="https://counter.theconversation.com/content/117713/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Scanlon receives funding from NSERC Canada. He is a member of the Board of Directors of AACCI - Cereals & Grains Association. </span></em></p>Measurement and standards are at the heart of how we trade commodities and measure wealth. So what happens now that the planet’s most critical standard has been completely overhauled?Martin Scanlon, Dean, Faculty of Agricultural and Food Sciences, University of ManitobaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1172552019-05-19T19:37:23Z2019-05-19T19:37:23ZThe way we define kilograms, metres and seconds changes today<figure><img src="https://images.theconversation.com/files/275076/original/file-20190517-69189-f6415j.jpg?ixlib=rb-1.1.0&rect=149%2C177%2C4932%2C3148&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A new standard defines the kilogram from today.</span> <span class="attribution"><span class="source">Shutterstock/Piotr Wytrazek </span></span></figcaption></figure><p>We measure stuff all the time – how long, how heavy, how hot, and so on – because we need to for things such as trade, health and knowledge. But making sure our measurements compare apples with apples has been a challenge: how to know if my kilogram weight or metre length is the same as yours.</p>
<p>Attempts have been made to define the units of measurement over the years. But today – <a href="http://www.worldmetrologyday.org/">International Metrology Day</a> – sees the <a href="https://www.bipm.org/en/measurement-units/rev-si/">complete revision</a> of those standards come into play.</p>
<p>You won’t notice anything – you will not be heavier or lighter than yesterday – because the transition has been made to be seamless. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-what-is-mass-49299">Explainer: what is mass?</a>
</strong>
</em>
</p>
<hr>
<p>Just the definitions of the seven base units of the <a href="https://www.bipm.org/en/measurement-units/">SI</a> (Système International d'Unités, or the International System of Units) are now completely different from yesterday.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275067/original/file-20190517-69174-kx7jf6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">New definitions of the (SI) standards for the kilogram (kg), metre (m), second (s), ampere (A), kelvin (K), mole (mol) and candela (cd).</span>
<span class="attribution"><a class="source" href="https://www.bipm.org/en/si-download-area/graphics-files.html#">BIPM</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>How we used to measure</h2>
<p>Humans have always been able to count, but as we evolved we quickly moved to measuring lengths, weights and time.</p>
<p>The Egyptian Pharaohs caused pyramids to be built based on the length of the royal forearm, known as the Royal Cubit. This was kept and promulgated by engineer priests who maintained the standard under pain of death.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=312&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=312&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=312&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=393&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=393&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274858/original/file-20190516-69195-1v3habt.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=393&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Metrology in action – weighing the souls of the dead and the Egyptian Royal Cubit (the black rod).</span>
<span class="attribution"><span class="source">Brynn Hibbert</span></span>
</figcaption>
</figure>
<p>But the cubit wasn’t a fixed unit over time – it was about half a metre, plus or minus a few tens of millimetres by today’s measure. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/written-in-stone-the-worlds-first-trigonometry-revealed-in-an-ancient-babylonian-tablet-81472">Written in stone: the world's first trigonometry revealed in an ancient Babylonian tablet</a>
</strong>
</em>
</p>
<hr>
<p>The first suggestion of a universal set of decimal measures was made by John Wilkins, in 1668, then Secretary of the Royal Society in London. </p>
<p>The impetus for doing something practical came with the French Revolution. It was the French who defined the first standards of length and mass, with two platinum standards representing the metre and the kilogram on June 22, 1799, in the Archives de la République in Paris.</p>
<h2>Agreed standards</h2>
<p>Scientists backed the idea, the German mathematician Carl Friedrich Gauss being particularly keen. Representatives of 17 nations came together to create the International System of Units by signing the <a href="https://www.bipm.org/en/worldwide-metrology/metre-convention/">Metre Convention treaty</a> on May 20, 1875.</p>
<p>France, whose street cred had taken a battering in the Franco-Prussian war and was not the scientific power it once was, offered a beaten-up chateau in the Forest of Saint-Cloud as an international home for the new system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274859/original/file-20190516-69174-1pddybz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">BIPM, home of the SI.</span>
<span class="attribution"><span class="source">Brynn Hibbert (2012)</span></span>
</figcaption>
</figure>
<p>The Pavilion de Breteuil still houses the Bureau International de Poids et Mesures (<a href="https://www.bipm.org/en/about-us/">BIPM</a>), where resides the International Prototype of the Kilogram (henceforth the Big K) in two safes and three glass bell jars.</p>
<p>The Big K is a polished block of platinum-iridium used to define the kilogram, against which all kilogram weights are ultimately measured. (The original has only been weighed three times against a number of near-identical copies.)</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=745&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=745&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=745&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=937&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=937&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275220/original/file-20190517-69178-rnekh0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=937&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">International prototype of the kilogram (the Big K).</span>
<span class="attribution"><span class="source">Photograph courtesy of the BIPM</span></span>
</figcaption>
</figure>
<p>The British, who had been prominent in the discussions and had provided the platinum-iridium kilogram, refused to sign the Treaty until 1884. </p>
<p>Even then the new system was only used by scientists, with everyday life being measured in traditional Imperial units such as pounds and ounces, feet and inches. </p>
<p>The United States signed the Treaty on the day, but then never actually implemented it, hanging on to its own version of the British Imperial system, which it still mostly uses today.</p>
<p>The US may have rued that decision in 1999, however, when the Mars Climate Orbiter (<a href="https://www.jpl.nasa.gov/missions/mars-climate-orbiter/">MCO</a>) went missing in action. The <a href="https://llis.nasa.gov/llis_lib/pdf/1009464main1_0641-mr.pdf">report into the incident</a>, quaintly called a “mishap” (which cost US$193.1 million in 1999), said:</p>
<blockquote>
<p>[…] the root cause for the loss of the MCO spacecraft was the failure to use metric units in the coding of a ground software file, “Small Forces”, used in trajectory models.</p>
</blockquote>
<p>Essentially the spacecraft was lost in the atmosphere of Mars as it entered orbit lower than planned. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=545&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=545&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=545&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=685&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=685&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275038/original/file-20190516-69189-6ha4gc.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=685&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Lost on Mars: An investigation found the Mars Climate Orbiter likely burned up in the atmosphere of the red planet due to a clash of metrics.</span>
<span class="attribution"><a class="source" href="https://www.jpl.nasa.gov/missions/mars-climate-orbiter/">NASA/JPL</a></span>
</figcaption>
</figure>
<h2>The new SI definitions</h2>
<p>So why the change today? The main problems with the previous definitions were, in the case of the <a href="https://www.bipm.org/en/bipm/mass/ipk/">kilogram</a>, they were not stable and, for the unit of electric current, the ampere, could not be realised.</p>
<p>And from weighings against official copies, we think the Big K was slowly losing mass.</p>
<p>All the units are now defined in a common way using what the BIPM calls the “<a href="https://www.bipm.org/en/measurement-units/rev-si/explicit-constant.html">explicit constant</a>” formulation. </p>
<p>The idea is that we take a universal constant – for example, the speed of light in a vacuum – and from now on fix its numerical value at our best-measured value, without uncertainty.</p>
<p>Reality is fixed, the number is fixed, and so the units are now defined.</p>
<p>We therefore needed to find seven constants and make sure all measurements are consistent, within measurement uncertainty, and then start the countdown to today. (All the technical details are <a href="https://www.bipm.org/en/measurement-units/rev-si/">available here</a>.)</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/275072/original/file-20190517-69195-odf7rf.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The seven unites are now defined by universal constants such as the speed of light <em>c</em> for the metre.</span>
<span class="attribution"><a class="source" href="https://www.bipm.org/en/si-download-area/graphics-files.html">BIPM</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Australia had a hand in fashioning the roundest macroscopic object on the Earth, a silicon sphere used to measure the <a href="https://www.nist.gov/si-redefinition/meet-constants">Avogadro constant</a>, the number of entities in a fixed amount of substance. This now defines the SI unit, mole, used largely in chemistry. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/274862/original/file-20190516-69195-1wqx8z5.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Walter Giardini of the National Measurement Institute Australia holding a silicon sphere as part of the Avogadro project.</span>
<span class="attribution"><span class="source">Brynn Hibbert</span></span>
</figcaption>
</figure>
<h2>From standard to artefact</h2>
<p>What of the Big K – the standard kilogram? Today it becomes an object of great historical significance that can be weighed and its mass will have measurement uncertainty. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-not-so-easy-to-gain-the-true-measure-of-things-92741">It's not so easy to gain the true measure of things</a>
</strong>
</em>
</p>
<hr>
<p>From today the kilogram is defined using the Planck constant, something that doesn’t change from quantum physics.</p>
<p>The challenge now though is to explain these new definitions to people – especially non-scientists – so they understand. Comparing a kilogram to a metal block is easy.</p>
<p>Technically a kilogram (kg) is <a href="https://www.bipm.org/en/CGPM/db/26/1/">now defined</a>:</p>
<blockquote>
<p>[…] by taking the fixed numerical value of the Planck constant <em>h</em> to be 6.626 070 15 × 10<sup>–34</sup> when expressed in the unit J s, which is equal to kg m<sup>2</sup> s<sup>–1</sup>, where the metre and the second are defined in terms of <em>c</em> and Δν<sub>Cs</sub>. </p>
</blockquote>
<p>Try explaining that to someone!</p>
<hr>
<p><em>Update: the phrase “tens of centimetres” was changed to “tens of millimetres” at the request of the author.</em></p><img src="https://counter.theconversation.com/content/117255/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Brynn Hibbert receives funding from ARC, International Union of Pure and Applied Chemistry (IUPAC). He is Past President of the Royal Society of New South Wales, Past Chair of the Analytical Division of IUPAC and present Secretary of the IUPAC Interdivisional Committee on Terminology Nomenclature and Symbols (ICTNS).</span></em></p>Today marks one of the biggest shake-ups in the history of measurement. But the new standards on how we define units of mass, length, time and so on are not easy to explain.David Brynn Hibbert, Emeritus Professor of Analytical Chemistry, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/927412018-12-13T19:12:09Z2018-12-13T19:12:09ZIt’s not so easy to gain the true measure of things<figure><img src="https://images.theconversation.com/files/250340/original/file-20181212-110240-lq38zl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some things are just tricky to measure.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/memotions/259656126/">Flickr/Patty O'Hearn Kickham</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>I teach measurement – the quantification of things. Some people think this is the most objective of the sciences; just numbers and observations, or what many people call objective facts.</p>
<p><a href="https://digital.nls.uk/scientists/biographies/lord-kelvin/discoveries.html">Lord Kelvin</a>, a famous British scientist, <a href="https://www.goodreads.com/quotes/166961-when-you-can-measure-what-you-are-speaking-about-and">said</a>:</p>
<blockquote>
<p>When you can measure what you are speaking about, and express it in numbers, you know something about it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.</p>
</blockquote>
<p>I generally agree.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-we-count-to-10-78034">Curious Kids: Why do we count to 10?</a>
</strong>
</em>
</p>
<hr>
<p>But – and you knew there was going to be a but – putting numbers on a thing may not be as objective as you may think. Possibly even more surprisingly, putting numbers on a thing may actually change that thing.</p>
<h2>Oh, the uncertainty</h2>
<p>The <a href="https://www.britannica.com/science/uncertainty-principle">Heisenberg’s uncertainty principle</a> says that at the quantum level, if you can quantify one aspect of a particle (say, its position) then you cannot quantify another (its momentum or where it is going).</p>
<p>There is a more general principle in physics called the Observer Effect that states for certain systems, the act of measuring something affects or changes that thing. </p>
<p>Author Douglas Adams noted this problem in his famous Hitchhiker’s Guide to the Galaxy series, in which he concluded the answer to <a href="http://hitchhikers.wikia.com/wiki/Ultimate_Question">the ultimate question about life, the universe and everything</a> could not exist in the same universe where the actual question existed. If you found the answer then the question would change.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=425&fit=crop&dpr=1 600w, https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=425&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=425&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=533&fit=crop&dpr=1 754w, https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=533&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/250360/original/file-20181213-110234-3ixma9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=533&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The ultimate answer is 42, but what’s the question?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/96092563@N08/29134856384/">Flickr/Max Sat</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>The act of measurement changing a thing goes beyond hard core physics or even hardcore science fiction, fantasy and comedy. Measurements can make changes to people.</p>
<p>From the psychologist and social scientist Donald Campbell, we get <a href="https://searchbusinessanalytics.techtarget.com/definition/Campbells-Law">Campbell’s Law</a>, which warns us that:</p>
<blockquote>
<p>The more any quantitative social indicator is used for social decision-making, the more subject it will be to corruption pressures and the more apt it will be to distort and corrupt the social processes it is intended to monitor.</p>
</blockquote>
<p>Ideally, quantitative social indicators are designed to monitor and help direct progress towards a goal, and so they should change our behaviour. But within a relatively short period, these quantifications can be gamed or manipulated (corrupted) to make some decisions or outcomes appear better than others.</p>
<p>This gaming is common in political debates, where reclassifications or careful re-sampling can change trends in, say, unemployment (under-employment?) or the <a href="https://www.abc.net.au/radionational/programs/the-economists/metrics/10499956">economy</a>.</p>
<p>Others do the same, for example, <a href="http://www.thedailyriff.com/articles/campbells-law-in-education-test-scores-vs-accountability-716.php">standard education scores for private versus public versus religious schools</a> – we have all heard about “<a href="http://www.bbc.com/news/education-41580550">teaching to the test</a>” or encouraging selected students to boycott the test.</p>
<p>Such manipulation eventually becomes obvious and often leads to the epithet of “<a href="http://www.twainquotes.com/Statistics.html">lies, damned lies and statistics</a>”. </p>
<h2>Oh, the corruption</h2>
<p>As someone who teaches statistics, I am offended on behalf of that noble art – because the problem is not statistics, but rather the way people have corrupted the measurements to make the numbers look better.</p>
<p>OK, it is easy to see how social measurements can be manipulated to make people think or act differently. This is especially true in the aftermath of the failure of social scientists and survey-takers to predict the outcomes of the <a href="https://theconversation.com/us-election-how-did-the-polls-get-it-so-wrong-68500">US elections</a> or <a href="https://theconversation.com/why-the-media-got-it-so-wrong-on-trump-and-brexit-68542">Brexit referendum</a>.</p>
<p>But what about hard scientific numbers? Take, for example, a person’s height. We can define it clearly and deal with anomalies (including things like posture, shoes, or the presence or absence of a large hairstyle), and we can easily measure thousands of individuals. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=476&fit=crop&dpr=1 600w, https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=476&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=476&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=598&fit=crop&dpr=1 754w, https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=598&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/250361/original/file-20181213-110234-3j93ww.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=598&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">‘Aren’t you a little short for a stormtrooper?’</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/pinkpurse/5276937996/">Flickr/Camille Rose</a></span>
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</figure>
<p>Good, hard and objective eh? We conclude that, on average, men are taller than women (which is the case in <a href="http://www.abs.gov.au/ausstats/abs@.nsf/lookup/4338.0main+features212011-13">Australia</a>, and elsewhere according to a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4961475/">2016 study</a>). There is no sexism implicit in this statement, although it does assume gender is strictly binary and ignores the possibility of non-binary groups like those of transgender.</p>
<p>But this simple conclusion often mutates into one that states men are taller than women, or that any random man is taller than any random woman. We have a mental image of men being taller than women and behave that way despite this only being true on average. </p>
<p>So, are men taller than women? It depends. <a href="http://www.guinnessworldrecords.com/world-records/tallest-woman">Zeng Jinlian</a> measured up at 246.3cm (8ft 1in) and although she died in 1982 she still holds the record as the tallest woman ever, and was taller than almost every male who has ever lived.</p>
<p>There is a greater than 50% chance that a man chosen at random will be taller than a randomly chosen woman, because that is what the common definitions of average mean.</p>
<p>But if the woman has a genetic heritage from the Netherlands and the man doesn’t, or if the women was born, say, in 1990 but the man was born earlier, then it is more likely the woman will be taller than the man – as average heights vary from country to country and have been on the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4961475">rise over the past century</a>). </p>
<p>You could make a bit of money playing the odds if you were betting against someone who always acted as if women were shorter than men.</p>
<p>The distribution of heights is quite complex (statistically speaking, it is non-normal, <a href="http://www.statisticshowto.com/probability-and-statistics/skewed-distribution/">skewed</a> or <a href="http://www.statiticshowtocom/heterogeneity/">heterogeneous</a>), so if it were actually “important” to get an itdividual’s relative height correct, an assumption than men are taller than women would be most inappropriate.</p>
<h2>So what to measure?</h2>
<p>So when is it important to measure the height of a human? Actually, this is related to the hardest question in the entire science of measurement – what do you choose to measure.</p>
<p>Two individuals who are the same total height may have different proportions of length in their <a href="http://www.guinnessworldrecords.com/world-records/longest-legs-female">legs</a> or their <a href="http://www.guinnessworldrecords.com/world-records/longest-neck">necks</a>, so measurements of one of these components may be more relevant depending on whether you are selling pants, skirts, dresses, shirts or earrings.</p>
<p>There is often little objectiveness in the selection of which thing to measure. Rather there are strong subjective elements that selects something to measure based on its familiarity, cost of measurement, perceived <a href="http://www.statisticshowto.com/probability-and-statistics/correlation-coefficient-formula/">correlation</a> with other parameters of interest. </p>
<p>We measure a person’s height (and weight) not because they tend to be directly relevant to anything but rather because they are easy to measure.</p>
<p>Height and weight are used to calculate our Body Mass Index (<a href="http://healthyweight.health.gov.au/wps/portal/Home/get-started/are-you-a-healthy-weight/bmi/">BMI</a>), often used as <a href="https://www.mydr.com.au/tools/bmi-calculator">a measure</a> of whether you’re overweight and unhealthy or not.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/250363/original/file-20181213-110228-uoip5f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The relationship between your height and weight is not always the best way to measure obesity.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/kizette/5804672027/">Flickr/Paola Kizette Cimenti</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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</figure>
<p>But <a href="https://www.betterhealth.vic.gov.au/health/healthyliving/body-mass-index-bmi">several factors can affect your BMI</a> and health, so a more useful measure of obesity might be your <a href="http://healthyweight.health.gov.au/wps/portal/Home/get-started/are-you-a-healthy-weight/waist-circumference/">waist circumference</a>.</p>
<p>In the ideal world, we would measure your body’s actual fat and its location (<a href="https://www.researchgate.net/publication/256985973_Ultrasound_as_a_Tool_to_Assess_Body_Fat">maybe using ultrasound</a>). </p>
<p>But we have a history of using BMI. It is cheap to do and there are industries set up around it, so we continue measuring that parameter.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-little-number-theory-makes-the-times-table-a-thing-of-beauty-40327">A little number theory makes the times table a thing of beauty</a>
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</em>
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<p>The consequence of using this indirect measurement is that actions are focused on reducing BMI, rather than on reducing the <a href="https://theconversation.com/explainer-how-does-excess-weight-cause-disease-7061">fat deposits that directly cause poor health</a>.</p>
<p>So, be careful what you choose to measure and only make your final choice after you have considered a significant number of alternatives. </p>
<p>And be even more careful when someone else uses their numbers to prove their case. Consider how easy it would have been to corrupt or misuse an index or an indirect measurement that is only weakly correlated to the thing of interest.</p><img src="https://counter.theconversation.com/content/92741/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cris Brack is a Senior Fellow of The Higher Education Academy. He does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no other affiliations beyond the academic appointments above.</span></em></p>How useful is the information you get from the measure of any thing? That depends on what you chose measure in the first place, and that’s not always clear.Cris Brack, Associate professor in forest measurement and management, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1068382018-11-14T18:06:46Z2018-11-14T18:06:46ZThe kilogram is being redefined – a physicist explains<figure><img src="https://images.theconversation.com/files/245563/original/file-20181114-194500-gn0w70.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/old-white-vintage-kitchen-scale-brass-1040010754">Stefan Rotter/Shutterstock</a></span></figcaption></figure><p>How much is a kilogram? 1,000 grams. 2.20462 pounds. Or 0.0685 slugs based on the old Imperial gravitational system. But where does this amount actually come from and how can everyone be sure they are using the same measurement?</p>
<p>Since 1889, countries who are members of the <a href="https://www.bipm.org/en/worldwide-metrology/cgpm/">General Conference on Weights and Measures</a> have agreed to use a standard block of metal – kept near Paris – to define the kilogram. But although the modern block is stored in a highly controlled environment, its weight can change by tiny amounts as wear and tear causes it to lose mass and dirt causes it to increase. To address this problem, scientists around the world have spent nearly two decades discussing how the kilogram could instead be defined in relation to constant measurements of nature. And now they have finally reached a decision.</p>
<p>The <a href="https://books.google.nl/books?id=FufDNJHvgFEC&pg=RA1-PA278&lpg=RA1-PA278&dq=18841+grains+grave&source=bl&ots=B8Aenskenh&sig=zanQ-d8GXWWN3q6bG2YBbh9bZOM&hl=en&sa=X&ved=0ahUKEwjy0-C5rr7MAhWBLMAKHcG2AhwQ6AEIKTAD#v=onepage&q=%22nom%20generique%20de%20grave%22&f=false">first kilogram</a> (originally called a grave) was defined in 1793 by a commission of the French Academy of Sciences, who wanted a better standard than the fixed amounts of grain that had traditionally been used. The commission decided that the new measure would be the mass of one cubic decimetre of distilled water at 4°C (the temperature at which water has its highest density under standard conditions). This had the advantage in that most properly equipped labs would be able to reproduce this standard. Subsequently, a prototype of this mass was cast in brass. </p>
<p>Unfortunately, this definition of mass depended upon another variable measurement, the metre. At this point, the metre was only provisionally defined as part of the distance from the North Pole to the equator. Once the value of the metre and the temperature of water at its densest were more accurately defined, the kilogram also had to be replaced. And a new prototype was cast in platinum to represent this mass. </p>
<p>Eventually, this was replaced with the international prototype kilogram (IKP) used today, cast from a mixture of platinum and iridium to make it very hard and prevent it reacting with oxygen. The IPK and six copies are kept by the International Bureau of Weights and Measures in the Pavillon de Breteuil, Saint-Cloud, near Paris in France to act as a reference to measure against. Copies of the IPK are transported across the world to ensure all participating countries use the same standard.</p>
<p>But even the modern IPK can gradually change in mass. Radically, the answer from the International Bureau of Weights and Measures is to overhaul the definitions of a kilogram, as well as all the other basic units of measurement used in science (known as SI units, from the French for international system).</p>
<p>Instead of measuring the kilogram against a block stored in a vault, we can define it based on precise values of constants of nature. Agreeing a definition has taken a long time because we needed to be able to measure these constants to <a href="https://www.bipm.org/utils/en/pdf/BIPM-strategic-plan-2018.pdf">exacting standards</a> with an uncertainty of 30 parts per billion (meaning the measurements are accurate to 0.00000003 of a unit).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/245568/original/file-20181114-194506-hgutu7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A copy of the international prototype kilogram.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Prototype_kilogram_replica.JPG">Japs88/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Scientists have actually already done this for time and length. A second is no longer a fraction of the time it takes the Earth to revolve, which can change as the globe speeds up or slows down. Instead, a second is <a href="https://www.scientificamerican.com/article/how-does-one-arrive-at-th/">now defined</a> by the time it takes for a certain amount of energy to be released as radiation from atoms of Caesium-133. Specifically, <a href="https://www.bipm.org/en/publications/si-brochure/second.html">one second equals</a> 9,192,631,770 transitions in the hyperfine ground state levels of Caesium-133. This is the same no matter when or where it is measured.</p>
<p>Scientists were then able to <a href="https://www.bipm.org/metrology/length/units.html">redefine the metre</a> in relation to the second and another natural constant, the speed of light in a vacuum (c), which scientists have calculated as 299,792,458 metres per second. So one metre is now the length travelled by light in 1/c seconds.</p>
<p>The new definition of the kilogram uses a measurement from another fixed value from nature, <a href="http://astronomy.swin.edu.au/cosmos/P/Planck%27s+Constant">Planck’s constant</a> (h), which will be defined as 6.62607015×10<sup>−34</sup> joule seconds. Planck’s constant can be found by dividing the amount of energy a particle of light or “photon” carries by its electromagnetic frequency.</p>
<p>The constant is usually measured in joule seconds but this can also be expressed as kilogram square metres per second. We know what a second and a metre is from the other definitions. So by adding these measurements, along with an exact knowledge of Planck’s constant, we can get a new, very precise definition of the kilogram. </p>
<h2>Other units</h2>
<p>Part of the reason creating the new definition has taken so long is because scientists have had to create <a href="https://www.scientificamerican.com/article/the-kilogram-may-be-redefined/">very precise devices</a> to measure Planck’s constant with a high enough degree of accuracy. The method has also been controversial because it will break the link that the kilogram has to other base SI units, particularly <a href="https://physics.nist.gov/cuu/Units/mole.html">the mole</a>, which measures the amount of a substance in terms of the number of particles it’s made from. Some scientists have proposed <a href="http://iopscience.iop.org/article/10.1088/0026-1394/49/4/487/">alternative methods</a> as a result.</p>
<p>But following a symbolic vote, the new definition of the kilogram will be used by the International Bureau of Weights and Measures and national measurement institutes around the world, along with <a href="https://www.bipm.org/utils/en/pdf/CGPM/Convocation-2018.pdf#page=30">new definitions</a> of several other base SI units, the mole, the kelvin (temperature) and the ampere (current).</p>
<p>For most people, everyday life will carry on as normal despite the redefinitions. One standard bag of sugar will contain as much sugar as it ever did. But some of these changes, for example to the kelvin, will mean <a href="https://www.bipm.org/wg/CCT/TG-SI/Allowed/Documents/Report_to_CIPM_2.pdf">practical advantages</a> for scientists making very precise measurements. And to answer the question “how much is a kilogram”, we will no longer have to compare blocks of platinum or worry about scratching them.</p><img src="https://counter.theconversation.com/content/106838/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kevin Pimbblet receives funding from STFC and the Royal Astronomical Society. </span></em></p>The international prototype kilogram keeps changing weight so scientists have come up with a new way to calculate.Kevin Pimbblet, Senior Lecturer in Physics, University of HullLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/999212018-11-07T11:39:09Z2018-11-07T11:39:09ZWhich country is best to live in? Our calculations say it’s not Norway<figure><img src="https://images.theconversation.com/files/237513/original/file-20180921-129850-e897k4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It's not the U.S., either.</span> <span class="attribution"><a class="source" href="https://www.pexels.com/photo/antique-antique-globe-antique-shop-antique-store-414916/">Pixabay</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Every year, the United Nations releases <a href="http://hdr.undp.org/en/composite/HDI">the Human Development Index</a>.</p>
<p>The HDI is like a country’s report card. In a single number, it tells policymakers and citizens how well a country is doing. This year, Norway was at the top of the class, while Niger finished last. </p>
<p>The index first appeared in 1990. Before then, a country’s level of development was measured solely by its economic growth. By taking non-economic dimensions of human well-being into account, the HDI revolutionized the idea of what was meant by countries becoming “more developed.” </p>
<p>The HDI has been wildly successful in <a href="http://hdr.undp.org/en/content/celebrating-human-development-success">changing the way people think</a> about the development process. However, it still <a href="https://doi.org/10.2307/2808029">suffers from</a> <a href="https://doi.org/10.1016/j.jdeveco.2012.01.003">real flaws</a>. There have been numerous attempts to do its job better, including <a href="https://onlinelibrary.wiley.com/doi/10.1111/padr.12205">one that we published on Nov. 6</a>.</p>
<p>Eliminating the flaws in the HDI make a substantial difference. For example, Denmark was ranked fifth in the world according to this year’s UN rankings, but our new index knocks it down to only 27th, switching places with Spain.</p>
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<h2>Problems with the HDI</h2>
<p>Human development can be devilishly hard to measure. The HDI considers changes in three domains: economics, education and health. (One alternative to the HDI, <a href="https://www.socialprogress.org/">the Social Progress Index</a>, combines data on 54 domains.)</p>
<p>In our view, the HDI has three main problems. First, it implicitly assumes trade-offs between its components. For example, the HDI measures health using life expectancy at birth and measures economic conditions using GDP per capita. So the same HDI score can be achieved with different combinations of the two. </p>
<p>As a result, the HDI implies a value of an additional year of life in terms of economic output. This value differs according to a country’s level of GDP per capita. Dig into the HDI and you will find whether it assumes an additional year of life is worth more in the U.S. or Canada, more in Germany or France, and more in Norway or Niger. </p>
<p>The HDI also struggles with the accuracy and meaningfulness of the underlying data. Average income could be high in a country, but what if most of it goes to a small elite? The HDI does not distinguish between countries with the same GDP per capita, but different levels of income inequality or between countries based on the quality of education. By focusing on averages, the HDI can obscure important differences in human development. Incorporating inaccurate or incomplete data in an index reduces its usefulness.</p>
<p>Finally, data on different domains may be highly correlated. For example, the GDP per capita and the average level of education in countries are strongly related. Including two highly correlated indicators may provide little additional information compared to just using one.</p>
<h2>Our indicator</h2>
<p>We propose a new index: <a href="https://onlinelibrary.wiley.com/doi/10.1111/padr.12205">the Human Life Indicator, or HLI</a>. </p>
<p>The HLI looks at life expectancy at birth, but also takes the inequality in longevity into account. If two countries had the same life expectancy, the country with the higher rate of infant and child deaths would have a lower HLI.</p>
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<p>This solves the problem of having contentious trade-offs among its components, because it has only a single component. It solves the problem of inaccurate data, because <a href="https://doi.org/10.3386/w16572">life expectancy is the most reliable component</a> of the UN’s index. Because GDP per capita, the level of education and life expectancy are closely related to one another, little information is lost by using a human development indicator based only on life expectancy. </p>
<p>Our index draws a different picture than the one made by the HDI. Based on data from 2010 to 2015, Norway is not on top of the list in terms of human development. That honor goes to Hong Kong, while Norway drops to ninth place. Norway ranks highly on the HDI in part because of the revenues that it receives from North Sea oil and gas, but even with that revenue, Norway’s inequality-adjusted life expectancy is not the highest in the world. </p>
<p>What’s more, on our measure, Niger no longer is last. That dubious distinction goes to the Central African Republic.</p>
<p>The UN puts Canada and the U.S. as tied at 10th place, but Canada is ranked 17th in the world using our system, while the U.S. does poorly, ranking as 32nd. This relatively higher ranking of Canada reflects the higher longevity of its inhabitants and the lower inequality in their ages of death compared to people in the U.S.</p>
<p>In our view, the genius of the HDI is too important to give up, just because of problems with its implementation. In our new index, we have provided a simple approach that is free from the problems of the HDI. There is no need to have just one measure of human development, but it is useful to have at least one without contentious flaws.</p><img src="https://counter.theconversation.com/content/99921/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Warren Sanderson receives funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement No 323947. Project Name: Reassessing Aging from a Population Perspective, Re-Ageing. Warren Sanderson is a senior research scientist at the International Institute for Applied Systems Analysis in Laxenburg, Austria and a Professor of Economics, emeritus at Stony Brook University, Stony Brook, New York, USA.</span></em></p><p class="fine-print"><em><span>Sergei Scherbov receives funding from European Research Council (ERC) under the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement No 323947. Project Name: Reassessing Aging from a Population Perspective, Re-Ageing.</span></em></p><p class="fine-print"><em><span>Simone Ghislandi receives funding from the European Research Council (ERC) under the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement No 323947. Project Name: Reassessing Aging from a Population Perspective, Re-Ageing.</span></em></p>Most researchers use the UN’s Human Development Index to measure each country’s progress, but that system has flaws. A new, simplified index aims to do it better.Warren Sanderson, Professor of Economics, Stony Brook University (The State University of New York)Sergei Scherbov, Deputy Director of World Population Program, International Institute for Applied Systems Analysis (IIASA)Simone Ghislandi, Associate Professor of Social and Political Sciences, Bocconi UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1010652018-08-07T10:43:46Z2018-08-07T10:43:46ZThe US needs to get over its obsession with GDP<p><a href="https://www.bea.gov/newsreleases/national/gdp/gdpnewsrelease.htm">The Bureau of Economic Analysis</a> on July 27 released the GDP growth rate for the second quarter of 2018: 4.1 percent. </p>
<p>GDP – or gross domestic product – is the rate at which the total value of goods and services produced in the U.S. grew. Together with unemployment and inflation, it usually receives a lot of attention as an indicator of economic performance in the U.S. </p>
<p>There was much celebration over the 4.1 percent rate, as this is higher than that experienced in recent years, but <a href="https://www.nytimes.com/2018/07/26/business/economy/economy-gdp-trump.html">some in the media</a> questioned its sustainability. </p>
<p>That raises another critical question: Does it mean the economy is doing well and there is economic progress? While it is convenient to focus on one number, it turns out GDP alone is inadequate to measure the economic performance of a country. I have spent much of my working life studying economic well-being at the level of individuals or families, which offers a lens on the economy that is complementary to GDP.</p>
<h2>GDP problems</h2>
<p>GDP has <a href="http://ec.europa.eu/eurostat/documents/118025/118123/Fitoussi+Commission+report">many limitations</a>. It captures only a very narrow slice of economic activity: goods and services. It pays no attention to what is produced, how it is produced or how it might improve lives. </p>
<p>Still, many policymakers, analysts and reporters remain fixated on the GDP growth rate, as if it encapsulates all of a nation’s economic goals, performance and progress. </p>
<p>The obsession about GDP comes, in part, from the misconception that economics only has to do with market transactions, money and wealth. But the economy is also about people. </p>
<p>For example, for most U.S. workers, real earnings – after inflation is taken into account – <a href="https://fred.stlouisfed.org/series/LES1252881600Q">have been flat for decades</a>, whether GDP or the unemployment rate grew or not. Yet the attention has remained stuck on GDP.</p>
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<p>Despite the media’s obsession with GDP, many economists would agree that economics considers wealth or the production of goods and services as means to improve the human condition. </p>
<p>Over the past couple of decades, a number of international commissions and research projects have come up with ways to go beyond GDP. In 2008, the French government asked two Nobel prize winners, Joseph Stiglitz and Amartya Sen, as well as economist Jean-Paul Fitoussi, to put together an international commission of experts to come up with new ways to measure economic performance and progress. In <a href="http://ec.europa.eu/eurostat/documents/118025/118123/Fitoussi+Commission+report">their 2010 report</a>, they argued that there is a need to “shift emphasis from measuring economic production to measuring people’s well-being.” </p>
<h2>Complementary measures</h2>
<p><a href="https://www.insee.fr/en/information/2662494">One approach</a> is to have a dashboard of indicators that are assessed on a regular basis. For instance, workers’ earnings, the share of the population with health insurance and life expectancy could be monitored closely, in addition to GDP. </p>
<p>However, this dashboard approach is less convenient and simple than having one indicator to measure progress against. A wide set of indicators are in fact available already in the U.S. – but attention remains stuck on GDP.</p>
<p><a href="https://www.insee.fr/en/information/2662494">Another approach</a> is to use a composite index that combines data on a variety of aspects of progress into a single summary number. This single number could unfold into a detailed picture of the situation of a country if one zooms into each indicator, by demographic group or region. </p>
<p>One challenge is to select the dimensions that should be covered. Through an international consultative process, <a href="http://ec.europa.eu/eurostat/documents/118025/118123/Fitoussi+Commission+report">the commission led by Sen, Stiglitz and Fitoussi</a> defined eight dimensions of individual well-being and social progress, including health; education; political voice and governance; social connections and relationships; and the environment.</p>
<p>The production of such composite indices has flourished. For example, in 2011, the Organization for Economic Cooperation and Development launched the <a href="http://www.oecdbetterlifeindex.org/#/11111111111">Better Life Index</a>, covering housing, income, jobs, education, health, environment, community, civic engagement and work life balance.</p>
<p>The <a href="http://hdr.undp.org/en/content/human-development-index-hdi">Human Development Index of the United Nations</a>, started in 1990, covers income per capita, life expectancy at birth and education. This index shows how focusing on GDP alone can mislead the public about a country’s economic performance. The U.S. <a href="https://stats.oecd.org/index.aspx?DataSetCode=PDB_LV">ranks first internationally on GDP per capita</a>, but is in <a href="http://hdr.undp.org/en/2016-report">10th place</a> on the Human Development Index due to relatively lower life expectancy and years of schooling compared to other countries at the top of the list, like Australia.</p>
<p>I believe the U.S. obsession around GDP should stop. Changing how we track economic progress – by also closely monitoring composite indexes of well-being – isn’t about making the measurement of the economy more complicated and keeping economists fully employed. Rather, it’s about monitoring and delivering on the promise of socioeconomic progress.</p><img src="https://counter.theconversation.com/content/101065/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sophie Mitra does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Economists, politicians and the media watch GDP closely. But it isn’t the best way to measure the health of the US economy.Sophie Mitra, Professor of Economics, Fordham UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/777992017-05-29T20:07:54Z2017-05-29T20:07:54ZMelting ice and satellites: how to measure the Earth’s ‘wiggle’<figure><img src="https://images.theconversation.com/files/171080/original/file-20170526-23234-dor2t3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists use satellite sensing to find the Earth's centre of mass.</span> <span class="attribution"><a class="source" href="https://www.nasa.gov/image-feature/goddard/lro-earthrise-2015">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>In a driverless future, it will be vital that our cars know exactly where they are on the road, down to the millimetre. We’ve found that our current methods of measuring location may not be up to scratch. Changes on Earth’s surface, including polar ice melt, may alter its centre of mass, throwing our calculations out of whack. </p>
<p>Accurately pinpointing a location with a global positioning system (<a href="https://theconversation.com/explainer-what-is-gps-12248">GPS</a>) can only be done relative to Earth’s centre. Because we can’t reach the centre ourselves, scientists have to use satellite sensing to indirectly measure its location, and how it moves. </p>
<p>It’s a complicated task because the globe is not a perfect sphere nor uniformly made of the same material. Significant changes on its surface, such as melting snowpack, may also shift its centre of mass.</p>
<p>This means the centre of Earth essentially “wiggles”, but current measurement methods don’t accurately measure season-to-season variations that occur due to water movement. They also assume that its long-term motion can be described by the fit of a straight line. We believe that much more work needs to be done.</p>
<h2>The centre of the Earth is on the move</h2>
<p>The centre of Earth’s mass may not necessarily be close to its geometric centre. </p>
<p>To put it another way, while a cannonball’s centre of mass will be at its exact geometric centre, a pineapple’s centre of mass is closer to its heavier end. </p>
<p>It’s the same for Earth’s centre of mass: it will be closer to heavier loads on the surface and within Earth itself. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/169871/original/file-20170518-24341-3e6xtf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/169871/original/file-20170518-24341-3e6xtf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=549&fit=crop&dpr=1 600w, https://images.theconversation.com/files/169871/original/file-20170518-24341-3e6xtf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=549&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/169871/original/file-20170518-24341-3e6xtf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=549&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/169871/original/file-20170518-24341-3e6xtf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=690&fit=crop&dpr=1 754w, https://images.theconversation.com/files/169871/original/file-20170518-24341-3e6xtf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=690&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/169871/original/file-20170518-24341-3e6xtf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=690&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Processes that cause the surface of the Earth to deform at decadal scales.</span>
<span class="attribution"><span class="source">Anna Riddell</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Water can be a “heavier load”, both in the oceans, rivers and atmosphere, and in its solid form as ice sheets, glaciers and snow. High water levels in the Northern Hemisphere due to massive snowfall and rain over Canada and Europe <a href="https://earthobservatory.nasa.gov/GlobalMaps/view.php?d1=MOD10C1_M_SNOW">during the winter</a>, for example, change as the seasons transition into summer. </p>
<p>This matters when measuring Earth’s centre of mass. Take a ridiculously heavy cyclist, for example. As the cyclist travels over the surface of the Earth, the centre of Earth’s mass moves, as a balancing act. In the same way, as snow melts in the Northern Hemisphere spring and flows into the oceans, the Earth’s centre of mass may move away from the Northern Hemisphere. </p>
<p>As we monitor changes to land ice in Antarctica and Greenland, as well as the smaller mountain glaciers, we can also see changes in the motion of Earth’s centre of mass. </p>
<p>As some of this ice melt is due to human activity warming the atmosphere and ocean, humans may be indirectly changing the centre of mass of the entire planet.</p>
<h2>How we find the centre</h2>
<p>The centre of Earth has historically been measured by shooting powerful lasers to <a href="https://theconversation.com/space-bling-jewelled-lageos-satellites-help-us-to-measure-the-earth-76948">reflective satellites</a> in orbit. By tracking these small “golf ball” satellites, we can estimate Earth’s centre of mass and its small variations. </p>
<p>The movement of Earth’s centre of mass can also be estimated by tracking changes in gravity, as sensed by twin satellites chasing each other called the Gravity Recovery and Climate Experiment (<a href="https://grace.jpl.nasa.gov/news/89/grace-mission-15-years-of-watching-water-on-earth/">GRACE</a>). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/171078/original/file-20170526-23227-gb0abn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171078/original/file-20170526-23227-gb0abn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171078/original/file-20170526-23227-gb0abn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171078/original/file-20170526-23227-gb0abn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171078/original/file-20170526-23227-gb0abn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171078/original/file-20170526-23227-gb0abn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171078/original/file-20170526-23227-gb0abn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">NASA’s fleet of 18 Earth science missions in space, including GRACE.</span>
<span class="attribution"><a class="source" href="https://www.nasa.gov/topics/earth/images/index.html">NASA</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p><a href="http://onlinelibrary.wiley.com/doi/10.1002/2016JB013698/abstract">We found</a> that the two approaches, both the “golf ball” satellites and models with GRACE data, show movement of a few millimetres of Earth’s centre of mass. This is due to seasonal snowfall, but also the result of longer-term changes occurring because of increased ice melt and movements within planet itself, such as shifts in Earth’s mantle. </p>
<p>The two approaches also show differences in the amount and style of movement, which suggest that we cannot yet be totally confident we really know where the centre of mass is and how it is moving.</p>
<p>Our research also estimates that the long-term motion of Earth’s centre of mass has a banana-like bend rather than travelling in a straight line, but it’s not yet clear if that’s real or not. </p>
<p>As we gather more information and the demand for GPS exactness increases, our assumptions about how the centre is measured will need to change.</p>
<h2>Why we need to know where we’re going</h2>
<p>Because GPS measures relative to the centre of mass, any uncertainty in our knowledge of where the centre of Earth is and how it moves reduces its accuracy.</p>
<p>Improvements will come through more careful interpretation of satellite laser ranging measurements and long-term, stable funding of these global observatories, including those in <a href="http://www.ga.gov.au/scientific-topics/positioning-navigation/geodesy/geodetic-techniques/satellite-laser-ranging-slr">Australia</a>.</p>
<p>But improved knowledge of the location of the centre of Earth is just one part of ongoing efforts to improve the accuracy of our positioning. We also need to keep track of the <a href="https://theconversation.com/australia-on-the-move-how-gps-keeps-up-with-a-continent-in-constant-motion-71883">tectonic movement of Australia</a>, for example. Even distant <a href="https://theconversation.com/did-the-earth-move-for-you-how-gps-tracks-the-slow-movements-of-a-world-in-motion-55234">earthquakes</a> can change the shape of the land <a href="http://onlinelibrary.wiley.com/doi/10.1002/jgrb.50154/abstract">by amounts that matter</a>. </p>
<p>If we’re to know exactly where we are, our methods for measuring Earth’s centre need an overhaul.</p><img src="https://counter.theconversation.com/content/77799/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anna Riddell receives funding from Geoscience Australia. </span></em></p><p class="fine-print"><em><span>Matt King receives funding from The Australian Research Council and Department of Environment. </span></em></p>Driverless cars and drones will require pinpoint location accuracy, which means our methods for measuring the Earth’s centre need an overhaul.Anna Riddell, Geodesy PhD Candidate, University of TasmaniaMatt King, Professor, Surveying & Spatial Sciences, School of Land and Food, University of TasmaniaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/706422017-01-05T21:06:57Z2017-01-05T21:06:57ZIn a world awash with data, is the census still relevant?<p><em>How we track our economy influences everything from government spending and taxes to home lending and business investment. In our series <a href="https://theconversation.com/au/topics/the-way-we-measure-34466">The Way We Measure</a>, we’re taking a close look at economic indicators to better understand what’s going on.</em></p>
<hr>
<p>The Australian Census came under intense scrutiny in the wake of <a href="https://theconversation.com/au/topics/censusfail-30048">#censusfail</a>. Parliament conducted a <a href="http://parlinfo.aph.gov.au/parlInfo/download/publications/tabledpapers/a41f4f25-a08e-49a7-9b5f-d2c8af94f5c5/upload_pdf/Review%20of%20the%202016%20eCensus%20-%20final%20report.pdf;fileType=application%2Fpdf#search=%22publications/tabledpapers/a41f4">review</a>, the Senate an <a href="http://www.aph.gov.au/Parliamentary_Business/Committees/Senate/Economics/2016Census/Report">inquiry</a>, and <a href="http://www.theaustralian.com.au/opinion/columnists/judith-sloan/census-2016-we-dont-need-it-so-why-persist/news-story/a21d99e9c968136442a141fd1a80ea16">some in the media</a> questioned the entire point. </p>
<p>But cost and <a href="https://theconversation.com/census-2016-should-you-be-concerned-about-your-privacy-63206">privacy concerns</a> aside, population is one of the three <a href="http://www.treasury.gov.au/%7E/media/Treasury/Publications%20and%20Media/Publications/2015/2015%20Intergenerational%20Report/Downloads/PDF/2015_IGR.ashx">pillars</a> of the economy. </p>
<p>Understanding population characteristics is vital to inform us of challenges and opportunities, and is a necessary input in other economic indicators. The quality and timely population data found in the census is not gathered through any other means. If changes need to be made, it’s in the discussion around the census.</p>
<h2>So we know who is where</h2>
<p>The census is unique in that it is a total survey of the population, covering a range of social and economic variables. At present, it is the only way such data is obtained in Australia. </p>
<p>Without the census, we wouldn’t know how many we are, who we are and where we live. This means important planning and policy issues couldn’t be addressed. The location of schools and hospitals, provision of medical facilities, funding for major infrastructure would all be done without an accurate idea of who is where. </p>
<p>In fact, local, state and federal governments rely heavily on data only available in the census. The number of children, working age population, travel to work information, occupations, housing suitability and vulnerable populations is all data only found in the census.</p>
<p>The census also allows for sub-national analyses to be performed, particularly <a href="https://www.legislation.gov.au/Details/C2015C00247">legislated</a> population estimates and projections. These estimates form the basis of economic indicators such as labour force statistics and <a href="https://theconversation.com/its-good-the-government-will-report-gdp-per-capita-but-it-shouldnt-stop-there-69638">gross domestic product per capita</a>.</p>
<p>The estimates and projections also highlight <a href="http://www.theage.com.au/comment/the-age-editorial/victorias-twospeed-economy-slumping-regions-need-urgent-policy-response-20161208-gt71z6.html">inequalities</a> within society, and provide opportunities for policy responses and development at a regional level.</p>
<p>But the purpose of taking a <a href="http://unstats.un.org/unsd/demographic/meetings/egm/NewYork/2014/P&R_Revision3.pdf">census</a> goes beyond informing resource allocation, taxation and electoral representation. </p>
<p>The statistical benchmarks used in surveys and studies, research and analysis, and, most importantly, lower level aggregates and groups of interest can only be informed by census data. Low level aggregates allow identification of need. Identification of areas with high proportions of young people who cannot access employment or education can provide much insight into barriers to economic participation.</p>
<p>Quality information about homelessness, minorities, and Indigenous populations is only truly obtained via a census.</p>
<h2>The data we already collect won’t do</h2>
<p>One of the <a href="http://www.theaustralian.com.au/opinion/columnists/judith-sloan/census-2016-we-dont-need-it-so-why-persist/news-story/a21d99e9c968136442a141fd1a80ea16">arguments against the census</a> is that we can get the same data elsewhere from the multitude of service providers that already come in contact with the public. </p>
<p>The problem is that these data collections are administrative. They’re collected for a reason and with limited scope. </p>
<p>Centrelink data is collected to provide a service. Information we provide to the tax office ensures tax compliance. Medicare doesn’t keep information about overseas nationals and people who have never had their birth registered, which is an issue in remote and Indigenous communities.</p>
<p>Australia’s large immigrant population would become a blind spot if we were to rely on the data the government already collects, as many aren’t eligible for certain government services. The data collected by Centrelink, the tax office and Medicare don’t provide sufficient scope. So far the census is the only data source that fits the bill.</p>
<h2>Some alternatives</h2>
<p>Population registers are a viable alternative to our five-yearly censuses. Finland uses a <a href="http://vrk.fi/en/population-information-system">computerised system</a> to record population data including births, deaths, marriages, migration and so on. The Netherlands, on the other hand, conducts a <a href="https://www.youtube.com/watch?v=SLpDkcyenf0">virtual census</a> by pulling together digital data from a number of different sources. </p>
<p>These registers offer real-time data, but they require ongoing maintenance and verification and often exceed the <a href="http://unstats.un.org/unsd/demographic/meetings/egm/NewYork/2014/P&R_Revision3.pdf">cost</a> of our census. Ironically, they also need to be checked against a census. And Germany’s experience shows population registers are not always <a href="http://www.nytimes.com/2013/06/01/world/europe/census-shows-new-drop-in-germanys-population.html">accurate</a>. </p>
<p>Further, major legislation changes would have to go through for Australia to be able to pool data like this. The establishment of a national population register would be costly and demand interdepartmental government coordination.</p>
<p>We could also look to the United States’ method of conducting surveys in between a 10-yearly census. This mixed methodology was suggested by the ABS in <a href="http://www.smh.com.au/federal-politics/political-news/abbott-government-considers-axing-the-australian-census-to-save-money-20150218-13ieik">2015</a> to cut costs.</p>
<p>However, limited financial upside, together with lower quality data, makes it a risky alternative for Australia. Plus we shouldn’t think of the census as an unrecoverable cost. The Office of National Statistics in the United Kingdom estimated the costs of their 2011 census were <a href="https://www.unece.org/fileadmin/DAM/stats/documents/ece/ces/ge.41/2015/mtg1/D1_1110_Value_of_the_census__ONS_.pptx">recovered</a> in just over a year.</p>
<h2>The future is data</h2>
<p>So how can we improve our census?</p>
<p>Online census completion will save money, improve data quality and reduce data processing time. However, online collection must be balanced to ensure disadvantaged populations aren’t excluded. The end of the census collector hasn’t arrived just yet.</p>
<p>More importantly, we must define contemporary data needs moving into the future. An informed public conversation about migration, employment, families and our changing population is much needed to gain <a href="http://datafutures.co.nz/our-work-2/talking-to-new-zealanders/social-licence/">social licence</a> to collect and use relevant data. </p>
<p>Whether the methodology of census continues as is or we introduce an alternative method of data collection, the key going forward is the question of legitimacy. Steps must be taken to justify the need to take a census, and to assuage privacy and security concerns. Without social license we’ll see the failings of the 2016 census play out over and over again.</p>
<p>Australia’s future relies on strong evidence we can agree on. This isn’t solely the domain of researchers. We all have a stake.</p><img src="https://counter.theconversation.com/content/70642/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Liz Allen worked at the Australian Bureau of Statistics (ABS) between 2006 and 2007. Liz has no ongoing employment or financial links with the ABS. Liz is a user of ABS data for research purposes.</span></em></p>The Australian Census has been taken since 1911. But is it still necessary in today’s world of mass digital data collection?Liz Allen, Postdoctoral Fellow, Centre for Aboriginal Economic Policy Research, Australian National UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/686722017-01-03T20:13:46Z2017-01-03T20:13:46ZHow and why we are moving beyond GDP as a measure of human progress<figure><img src="https://images.theconversation.com/files/150422/original/image-20161216-26056-d8t89s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Accessible "green space" in cities is one of the things we will start measuring.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><em>How we track our economy influences everything from government spending and taxes to home lending and business investment. In our series <a href="https://theconversation.com/au/topics/the-way-we-measure-34466">The Way We Measure</a>, we’re taking a close look at economic indicators to better understand what’s going on.</em></p>
<hr>
<p>Ever since 1944, Gross Domestic Product (GDP) has been a primary measure of economic growth. It’s in the news regularly and, even though few can define what it means, there is general acceptance that when GDP is growing, things are good. </p>
<p>There are problems with this simplistic formulation. </p>
<p>GDP measures production only. It does not capture <a href="https://theconversation.com/over-fishing-is-strangling-a-key-protein-source-for-west-africans-64498">collapsing fish stocks</a>, <a href="https://theconversation.com/fat-nation-why-so-many-australians-are-obese-and-how-to-fix-it-23783">increasing obesity</a> and <a href="https://theconversation.com/type-2-diabetes-increasingly-affects-the-young-and-slim-heres-what-we-should-do-about-it-61283">diabetes</a>, or new types of <a href="https://theconversation.com/is-australia-really-being-flooded-by-new-killer-drugs-64426">synthetic drugs</a>. When people choose to work part-time to have a better work-life balance, GDP actually goes down. </p>
<p>This narrow focus distorts our perception of progress. It guides our representatives to focus only on certain things – what is measured – and allows them to ignore what isn’t quantified and regularly reported.</p>
<p>But a new set of measures is slowly being established, which aims to capture a wider range of human experiences and reset our idea of “success”. Called the UN Sustainable Development Goals (SDGs), these aim to include all the main pillars of a progressive society, from physical safety through to economic opportunity and good health.</p>
<p>SDGs will force action by highlighting what is currently covered up by the narrow measures of how our economy and society are faring.</p>
<h2>A new way of framing progress</h2>
<p>The SDGs arose out of the <a href="https://theconversation.com/how-the-millennium-development-goals-failed-the-worlds-poorest-children-44044">expiration of the Millennium Development Goals</a> in 2015 (which focused primarily on poverty reduction). Out of a growing awareness of the ecological limits of the planet, and a desire to ensure that progress is fair and accessible to all people, attempts were made at creating a comprehensive set of national goals for all nations.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=278&fit=crop&dpr=1 600w, https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=278&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=278&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=349&fit=crop&dpr=1 754w, https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=349&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/149800/original/image-20161213-1625-vyh5lo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=349&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">UN Sustainable Development Goals.</span>
<span class="attribution"><a class="source" href="http://www.un.org/sustainabledevelopment/sustainable-development-goals/">UNDP</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Although the goals are non-binding, they have received unprecedented support. They were ratified by all member states of the <a href="http://www.un.org/sustainabledevelopment/blog/2015/09/historic-new-sustainable-development-agenda-unanimously-adopted-by-193-un-members/">UN General Assembly in 2015</a> and endorsed by international leaders such as <a href="http://w2.vatican.va/content/francesco/en/speeches/2015/september/documents/papa-francesco_20150925_onu-visita.html">Pope Francis</a> and <a href="http://qz.com/510680/bill-gates-united-nations-sustainable-development-goals/">Bill and Melinda Gates</a>. </p>
<p>The SDGs are accompanied by significant international diplomatic pressure. Each country is expected to commit resources and to gather and share data on progress towards each goal.</p>
<p>For decades, countries and international agencies, such as the <a href="http://apps.who.int/gho/data/node.home">World Health Organisation</a>, <a href="http://data.worldbank.org">World Bank</a>, <a href="http://hdr.undp.org/en/data">United Nations Development Program</a> and <a href="http://popstats.unhcr.org/en/overview">UNHCR</a>, have collected and shared data on various aspects of life. A mass of data has accumulated but never been organised into a framework that can be used as a national scorecard.</p>
<p>This leaves a substantial gap between the detailed data we have on the actual lives led by people around the world, and the indicator national governments use to measure progress.</p>
<h2>Measurement leads to action</h2>
<p>The focus on GDP leads to mantras such as <a href="http://budget.gov.au/2016-17/content/glossies/jobs-growth/html/jobs-growth-01.htm">“jobs and growth”</a> with an urgency that implies that there is not the time nor the resources to make economic growth fair or sustainable. Further, short election cycles make quick-grab economic gains more attractive than putting in place long-term plans for a more sustainable and fairer future.</p>
<p>Once there are set targets for goals like renewable energy we should expect that these issues will attract more attention from politicians. Once established and regularly reported, measures for targets like renewable energy and accessible green spaces in cities will create incentives for politicians to act. If they don’t, the public will have relevant information to track progress. </p>
<p>The SDGs are an important step to quantify and force progress.</p>
<h2>We’re under way</h2>
<p>Institutions with longer time horizons – universities, NGOs, statisticians and think tanks etc – are already on board. SDGs are now on the agenda of conferences across sectors of society from the <a href="http://www.farmers.org.au/content/nff/en/community/blog/SDGA16-our-common-wealth-our-global-future-171116.html">National Farmers Federation</a> through to the Australian Bureau of Statistics and the <a href="http://dfat.gov.au/aid/topics/development-issues/global-development-agenda/Pages/global-development-agenda.aspx">Department of Foreign Affairs and Trade</a>. They touch all sectors and every institution has a place within one of the goals. </p>
<p>With the goals and targets in place, work is being undertaken across institutional stakeholders to develop policy tools and <a href="http://www.sciencedirect.com/science/article/pii/S1462901116306712">frameworks</a>. This strengthens the opportunity for evidence-based policy that relies on past data, present benchmarking and quality evaluation. SDG networks and associations, such as <a href="http://ap-unsdsn.org/">SDSN Australia/Pacific</a>, have been formed to foster the development of the actual metrics. </p>
<p>SDGs will filter out to the public one headline and press release at a time. Expect to see headlines like “Norway, number 1 in education, what are they doing and what can we learn from it?”. Unlike our current metrics, the SDGs will be a common set of goals and measures able to track progress and provide real baselines and comparisons of what matters most.</p><img src="https://counter.theconversation.com/content/68672/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Tani Shaw does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>For a long time the way we measure what is going on in our economy and society has distorted our actions. We’re now building a more holistic way of measuring progress.Tani Shaw, PhD Scholar, Institute for Sustainable Futures, University of Technology SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/697902017-01-02T20:20:44Z2017-01-02T20:20:44ZExplainer: why markets care what businesses are buying<figure><img src="https://images.theconversation.com/files/148829/original/image-20161206-25738-r2500h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It's important to look at what businesses are purchasing.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p><em>How we track our economy influences everything from government spending and taxes to home lending and business investment. In our series <a href="https://theconversation.com/au/topics/the-way-we-measure-34466">The Way We Measure</a>, we’re taking a close look at economic indicators to better understand what’s going on.</em></p>
<hr>
<p>After all the geopolitical turmoil that gripped financial markets in 2016, some <a href="https://www.bloomberg.com/news/articles/2016-12-01/ten-good-pieces-of-economic-data-from-all-around-the-world">bright news</a> started to emerge as we approached the end of the year.</p>
<p>In economies from <a href="http://www.tradingeconomics.com/australia/manufacturing-pmi">Australia</a> to <a href="http://www.tradingeconomics.com/china/manufacturing-pmi">China</a>, <a href="http://www.tradingeconomics.com/germany/manufacturing-pmi">Germany</a> to the <a href="http://www.tradingeconomics.com/united-states/business-confidence">United States</a>, and even in perennial strugglers like <a href="http://www.tradingeconomics.com/italy/manufacturing-pmi">Italy</a> and <a href="http://www.tradingeconomics.com/japan/manufacturing-pmi">Japan</a>, the Purchasing Managers’ Index (PMI) is signalling an improvement in the economic outlook. </p>
<p>Historically, PMI has correlated closely with economic output. For example, the graph below shows that US PMI, produced by the <a href="https://www.instituteforsupplymanagement.org/ismreport/mfgrob.cfm?SSO=1">Institute for Supply Management</a> (ISM), closely aligns with US GDP growth, going all the way back to 1948. </p>
<p>But the real reason so many pay attention to PMI is that it is forward-looking – giving a good indication of where an economy is heading.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=414&fit=crop&dpr=1 600w, https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=414&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=414&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=521&fit=crop&dpr=1 754w, https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=521&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/148602/original/image-20161205-19399-1m4cmyv.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=521&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">United States ISM PMI (Manufacturing): author provided.</span>
</figcaption>
</figure>
<h2>What is the PMI?</h2>
<p>PMI is pieced together from a monthly survey of purchasing managers in several industries. Purchasing managers play an important role within a firm because they place advance orders for the raw materials that will drive output and corporate performance. As such, they have access to privileged information and are typically among the first to know when trading conditions are changing. </p>
<p>As a result, the PMI is a good indicator of the economic health of particular sectors in the economy. The manufacturing survey attracts most attention (and has the <a href="https://www2.gwu.edu/%7Eforcpgm/Bachman.pdf">greatest link</a> with economic output), but PMI is typically also available for the service and construction industries. </p>
<p>Several organisations produce PMI measures around the world. Although <a href="https://www.markiteconomics.com/public">Markit</a> tracks PMI across a number of countries, the <a href="https://www.aigroup.com.au/policy-and-research/economics/economicindicators/">Australian Industry Group</a> (AiG) PMI is most relevant for Australia. The most keenly watched and longest-standing international measure is provided by the American <a href="https://www.instituteforsupplymanagement.org/ismreport/mfgrob.cfm?SSO=1">ISM</a>.</p>
<h2>Calculating PMI</h2>
<p>The exact method of compiling the PMI differs slightly among institutions and across countries but is broadly similar.</p>
<p>Each month, a number of purchasing managers (e.g. 200 for AiG and 300 for the ISM) from a rotating sample of firms are surveyed. They are asked whether business activity has increased, decreased, or remained unchanged from the prior month. The survey also asks about specific business activities, like new orders, production, employment, supplier deliveries, and inventories. </p>
<p>The survey data is then used to create an index (in economic parlance this is called a <a href="http://www.investopedia.com/terms/d/diffusionindex.asp"><em>diffusion</em> index</a>). If all respondents claimed an improvement in business activity, then the index would be 100. If everyone said there has been a decline, then the index would be 0. Generally what we see is an index hovering around the 50 mark.</p>
<p>The common interpretation of this index, then, is that a number greater than 50 indicates an improvement in business activity, while a number less than 50 suggests a decline. Although the headline number is a <em>composite</em> of the various business activities, a more nuanced view of the business environment can be gained by looking at the sub-categories – the answers to the individual questions. </p>
<h2>The merits of the PMI</h2>
<p>The main difficulties with PMI are the same as those faced by any survey-based measure. The index relies on appropriate survey questions and truthfulness from respondents. Even then, it is possible that external events prevent intended activity from coming to fruition.</p>
<p>The key advantages of PMIs are that they are forward-looking in nature and timely – this owes much to the survey format. Published on a monthly cycle, the PMI gives a prompt indication of the direction of economic activity. It is available well in advance of the quarterly cycle of GDP figures (which are often subject to lags and large revisions) and provides details on new orders and inventory (in the sub-indexes). It can therefore be extremely useful in corporate decision-making. </p>
<p>As it is a survey of private firms, PMI is also not open to the <a href="http://www.economist.com/blogs/freeexchange/2015/07/chinese-economy">possible manipulation</a> encountered in official government statistics.</p>
<p>Other macroeconomic data may also indicate some of the things found in a PMI report. For instance, industrial production and the employment report may provide similar information to that contained in the PMI sub-indexes. </p>
<p>However, such measures typically take time to collate data and so are produced at a lag to PMI. They also generally reflect current (or past) information and so are not forward-looking. Further, the composite PMI provides a single number that is relatively straightforward for non-economists to understand. </p>
<p>In summary, measures of PMI are useful economic indicators that seem to track well with overall economic activity and are not comprehensively measured elsewhere. Given current PMI readings, even if risks remain, it appears that the global economy is on track to have a bright start to 2017.</p><img src="https://counter.theconversation.com/content/69790/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lee Smales does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If you’re into business and finance there are myriad numbers you can look at. But PMI is one of the better ones if you really want to know where an economy is going.Lee Smales, Associate Professor, Finance, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/376862015-02-19T10:54:58Z2015-02-19T10:54:58ZWhere do those snowfall totals on the news come from?<figure><img src="https://images.theconversation.com/files/72422/original/image-20150218-20793-1o5864s.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sometimes you don't need a measuring stick to come up with an assessment: really, really deep.</span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Route_292,shiga-kusatsu-road,shibu_pass,shibu-touge,kusatsu-town,japan.jpg">katorisi</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p><em>An updated version of this article was published on Jan. 27, 2022. <a href="https://theconversation.com/how-is-snowfall-measured-a-meteorologist-explains-how-volunteers-tally-up-winter-storms-175628">Read it here</a>.</em></p>
<p>The Blue Hill Observatory, a few miles south of Boston, recorded the deepest snow cover in its 130-year history a couple of years ago, an incredible 46 inches. In February 2015, Bangor, Maine tied its record for deepest snow at 53 inches. Mountainous locations will sometimes see triple-digit snow depths. </p>
<p>Impressive numbers for sure, but assuming you have a measuring stick long enough to reach the ground beneath all the white, really, how hard can it be to measure? You stick a ruler or yardstick into the snow and get a number, right? Well, not so fast. It’s a little more <a href="http://pqasb.pqarchiver.com/weatherwise/doc/200722527.html">complicated</a> than you might think to get those oh-so-important snow totals for winter storms.</p>
<p>Since 1890, the National Weather Service has relied on a network of volunteer observers, all strictly adhering to the <a href="http://www.nws.noaa.gov/om/coop/reference/Snow_Measurement_Guidelines.pdf">NWS guidelines</a>, to come up with snow measurement numbers over a region. There are over 8,700 <a href="http://www.nws.noaa.gov/om/coop/what-is-coop.html">cooperative observers</a> across the country who send in their weather data to the NWS daily, some who have done it for over <a href="http://www.srh.noaa.gov/tsa/?n=Coopawards">75 years</a>!</p>
<p>Snow measurement is inherently inexact, but attention to one’s surroundings and sticking to the guidelines help those of us who do it on a regular basis stay consistent – and with long-term weather records, consistency is arguably just as important as accuracy.</p>
<p>First, we do need to differentiate between snow <em>depth</em> and snow <em>fall</em>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72420/original/image-20150218-20773-f1jdo6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The author measuring the paltry three inches at his observation location in Pennsylvania. Note the instrument shelters in the background.</span>
<span class="attribution"><span class="source">Marisa Ferger</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>How deep is your snow</h2>
<p>Snow depth should be a measure of the average depth in a given location and its immediate surroundings. It’s usually rounded to the nearest whole number. To get a representative number, you need a site with minimal drifting (not always easy to find) and several measurements should be averaged to get a final number. I like 10 because it makes the math easy.</p>
<p>Careful measurement is vital so we can make reasonable estimates for the amount of liquid contained in the snowpack. As hard as it is to believe at times, the snow <em>will</em> eventually melt, and rapid melting could cause problems with flooding. Also, hydrologists’ models to predict water levels critically depend upon good initial data collection (though improved satellite data has helped reduce their reliance on any individual measurement).</p>
<p>Snow depth is like the sum of individual snowfalls, if one assumes no <a href="http://water.usgs.gov/edu/watercyclesublimation.html">sublimation</a> – snow turning into water vapor – or melting from the first snowfall until the present day. That assumption would almost always be wrong, of course, but if we suspend reality for a moment, the depth will still never exceed the sum of all snowfalls because snow is compressible. So, two 10.5-inch snowfalls may only accumulate to a depth of 17 inches. It’s the compressibility of snow that causes the greatest consternation and controversy with snowfall measurement.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72411/original/image-20150218-20802-mi3io2.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">National Weather Service snow board and snow measuring stick.</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:2013-10-14_12_27_14_National_Weather_Service_snow_board_and_snow_measuring_stick.JPG">Famartin</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>How much snow did a storm bring</h2>
<p>Snowfall is the amount of snow that accumulates during a given time, usually a 24-hour period. In a perfect world this 24-hour period would end at midnight, but the vast majority of National Weather Service cooperative observers take their daily observation in the morning. </p>
<p>To properly measure snowfall, you need a level and flat surface. As with snow depth, measuring snowfall should be unaffected by drifting. The National Weather Service suggests the use of a snowboard, which is a white surface that will absorb very little sunlight and stay close to the ambient air temperature, but any “cold” surface will do. Keeping in mind that consistency is critical, the goal here is to make a measurement that is representative of the surrounding area and consistent with others making snowfall measurements.</p>
<h2>More complicated cases…</h2>
<p>So, let’s consider three common scenarios. Here in the East, we often have to deal with snow that changes to rain during the course of a storm. Imagine 6.0 inches of snow falls, then an inch of sleet which compacts the snow to a 4-inch depth. Then, on top of that we have an inch of freezing rain which further compacts the snow to 2.6-inch depth by the end of the observation period. What should be listed as the daily snowfall? The snow depth?</p>
<p>In this situation, when the snow transitions to sleet, the snowboard should be cleared and the maximum depth of snow recorded, which is 6 inches in this case. Do the same with the sleet and this will add an inch to the snowfall (technically, “solid precipitation”) total. Freezing rain is never added to the daily snowfall total because it is in liquid form when it reaches the ground. Thus, the daily snowfall is 7.0 inches (measured to the nearest tenth of an inch) while the snow depth at observation is rounded to 3 inches.</p>
<p>In the case where, say, three heavy snow showers occur one afternoon, each dumping 1.5 inches before melting completely, the daily snowfall would be 4.5 inches with an observed depth of zero at the daily observation time. This assumes an observer is there to measure each short-lived accumulation. But because most observers are volunteers that’s not always the case, unfortunately.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/72421/original/image-20150218-20773-16d6xpz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Looks like a lot of snow – but how to quantify that?</span>
<span class="attribution"><a class="source" href="http://pixabay.com/en/snowy-street-deep-snow-winter-554957/">jill111</a></span>
</figcaption>
</figure>
<p>Finally, we come to the controversy. Let’s assume a steady snow falls for the entire 24-hour period at a rate of 2.0 inches per hour. If the snow board were cleared every hour, the daily snowfall would be 48.0 inches. But what if the observer could only be there at the daily observation time? By then the snow will have compacted some, depending upon the temperature and the amount of liquid in the snow, which can vary between about a quarter inch and three inches of liquid water for every 10" of snow.</p>
<p>This observer would log significantly less snowfall – for the exact same event – than the person who cleared the board every hour. This is a problem. The National Weather Service addresses it by mandating that no more than four snowfall measurements should be made in any 24-hour period. Ideally then, an observer who went to the snowboard every six hours and cleared 10.5 inches, 9.3 inches, 11.5 inches and 10.8 inches would get the officially correct snowfall measurement of 42.1 inches. </p>
<p>Several years ago, an observer in New York measured 77.0 inches of snow in a 24-hour period, which would have broken the record for heaviest one-day snowfall in U.S. history. However, it was <a href="http://www.weatheranswer.com/public/tughill.pdf">determined</a> that he cleared the snowboard much too frequently, thus inflating the daily total and invalidating the record.</p>
<p>Intrigue, suspense, mystery, controversy! So much more than just sticking a ruler in the snow. If it all sounds like a daily dose of meteorological fun to you, maybe you’ve got what it takes to volunteer for the NWS’s <a href="http://www.nws.noaa.gov/om/coop/index.htm">Cooperative Observer</a> program, where it’s not all about the white stuff. Daily high and low temperatures and precipitation of all forms are also measured, to strict NWS standards, of course.</p><img src="https://counter.theconversation.com/content/37686/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bill Syrett does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s really hard to measure snowfall accurately. The National Weather Service relies on more than 8,000 volunteers with rulers.Bill Syrett, Associate Teaching Professor of Meteorology and Atmospheric Science and Manager of the Joel N. Myers Weather Center, Penn StateLicensed as Creative Commons – attribution, no derivatives.