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What makes us happy? We analysed 200 years of written text to find the answer

Researchers used a statistical algorithm to analyse written texts between 1820-2009 in four Western countries. sirtravelalot/Shutterstock

How do you measure happiness? The answer to this question has eluded philosophers, scientists, and researchers for years. As happiness is a subjective feeling, it’s difficult to find a way of objectively measuring it. One of the most common methods for measuring happiness is through self-report surveys and polls, such as the UN’s World Happiness Report uses.

But when it comes to understanding how our happiness ranks when compared to previous generations, researchers have had an equally difficult time finding methods to measure it. Academics studying the past usually use a method called “close reading” – a thoughtful, critical analysis of a text – which allows them to gain a deeper understanding of how authors might have been feeling at the time they wrote these texts. Psychologists have confirmed this, and know that what a person says or writes can often reveal much about their underlying happiness.

But what if you could read every book that was ever written in order to develop an understanding of what it was really like to live through the last 200 years of history?

My colleagues and I recently conducted research that has taken a first step towards developing a quantitative picture of happiness throughout history. We developed a method that was able to analyse online texts from millions of fiction and non-fiction books and newspapers published over the past 200 years.

We did this by applying a statistical algorithm to millions of digitised historical texts in order to understand how happy writers were at the time of writing. This is called “sentiment analysis”, which measures how frequently an author uses positive and negative words to express their emotional attitude. More positive words, like “love”, “happiness”, and “celebration” indicate more positive feelings, whereas more negative words like “death”, “anger”, and “sadness” indicate negative feelings.

As some words have changed their meanings over time, we also took this into account when analysing words and their meanings. For example, words like “gay” and “risk” have changed their valence over time – in this case, both becoming more negative.

Read more: People with depression use language differently – here's how to spot it

By analysing the language used in written texts from four Western countries – the UK, US, Italy and Germany – we were able to create a quantitative picture of historical subjective well-being, which we called the “National Valence Index”.

The National Valence Index is able to compute the relative levels of happiness or unhappiness by looking at the language used in any text in any given year. By comparing this against the Eurobarometer survey data on subjective well-being, our measure appears to be reasonably reliable. We then use the National Valence Index to look at how wars, and economic and health changes over the last 200 years have impacted overall happiness.

Happiness then and now

What we found was remarkable. While gross domestic product (GDP) is often assumed to be associated with a rise in well-being, we found that its effect on well-being throughout history is marginal at best. GDP has increased fairly consistently over the last 200 years in the four countries that we looked at, but well-being has moved up and down dramatically over that time.

What is perhaps most remarkable is that well-being appears to be incredibly resilient to short-term negative events. Wars create dramatic valleys in well-being, but soon after the war well-being frequently recovers to its pre-war levels. Lasting changes to our measure of happiness occur slowly, over generations.

A time-series plot of the National Valence Index over the period 1820-2009. Courtesy of Thomas Hills, Daniel Sgroi, Chanuki Illushka Seresinhe and Eugenio Proto, Author provided (no reuse)

Our study found that Germany is at its happiest in the 1800s, and just after World War II. Similarly high values are also found in the other nations during the 1800s. However, these values might not be entirely accurate, as writers during the Victorian Age were typically of a higher class, and the topics they wrote about and language they used was different to now. Germany, however, has seen a rise in subjective happiness since the 1970s.

In the UK, the Winter of Discontent, in the late 1970s, is the lowest point of well-being and happiness we measured, which began to fall during the 1950s. The nation was happiest during the interwar years in the 1920s, and at the end of World War II.

In the US, happiness was affected by events such as the Civil War, the Great Depression, and the Korean War. The US was happiest in the 1920s, before the Great Depression and World War II caused well-being to plummet.

Italy was similarly affected by the world wars, but has seen a steady increase in subjective well-being since the 1970s.

These findings allow governments to better understand how they should form policies. For example, how should governments spend their money to improve happiness?

Across countries, an extra year of life (in terms of longevity) is equivalent to a 4.3% rise in GDP. A year of internal conflict is equivalent to a 30% drop in GDP. Policies that seek to enhance longevity, for example through providing better access to healthcare throughout life, may therefore be better than policies that only attempt to increase GDP, which is increasingly being challenged as a measure of progress.

The National Valence Index might also be used to understand how rising national debt and unemployment will influence our happiness in the future. A better understanding of what things positively and negatively effect society’s happiness could have measurable effects on both quality of life and a nation’s economic output. More generally, understanding our psychological past can help us to better envision a positive psychological future.

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