View from The Hill

When an economist politician plays with numbers, you can get some surprising results

Andrew Leigh with his earlier book Battlers and Billionaires. AAP/Alan Porritt

As books by or about present and former politicians rain down, Labor frontbencher Andrew Leigh, a one-time academic, has produced something for the superior trivia night.

The shadow assistant treasurer is the ultimate magpie in his discipline of economics. There is nothing he can’t explain by the dismal science, whatever might be said about damned lies and statistics. The Economics of Just About Everything might be a diversion as politics tragics chew over former Labor minister Greg Combet’s The Fights of My Life, Madonna King’s Hockey: Not Your Average Joe, and Mark Latham’s The Political Bubble, all out within a week.

Leigh had a special interest in the effect of the Howard gun buyback scheme, because of personal connections with two of Australia’s worst gun massacres. Hoddle Street killer Julian Knight is Leigh’s adopted second cousin (he’s never met him); one of the Port Arthur victims mentored Leigh at a law firm where he worked as a summer clerk.

The buyback had one “rock solid” result. Australia averaged more than one mass shooting a year (involving five or more people being killed) in the decade before the buyback – between 1987 and 1996, 94 victims were killed in mass shootings. In the decade after the legislation there wasn’t a mass shooting.

Leigh puts the chance of this being just luck at less than one in 100.

But actually the buyback reduced gun deaths mainly through fewer domestic shootings and suicides. Leigh and another researcher looked at whether places with more buybacks had a larger drop in gun homicide and suicide. The answer was yes.

With firearm suicide, the greatest reduction in weapons was in Tasmania, which had the biggest drop in these deaths. The smallest reduction in firearms per person was in Canberra, which saw the smallest drop in the firearms suicide rate. “Overall, we estimated that the Australian gun buyback saved at least 200 lives per year – mostly suicides.”

Leigh noted that one’s chances of being a victim of homicide in the late 2000s was about half what it had been in the late 1980s.

He has posited a couple of unexpected causes – legalised abortion and unleaded petrol – with Australia following US trends.

Although changes in the circumstances in which abortions could be legally performed (following court decisions) did not occur everywhere at the time, for more than two-thirds of the Australian population the change happened in the late ‘60s or early '70s – about 20 years before the crime rates dropped. There was “some evidence that the drop in homicide occurred first in the states that legalised abortion the earliest”.

The effect of legalising abortion, he says, has only a minor effect on the number of children born. “The main effect is not that families have fewer children, but rather that all of these children are born when the parents feel ready to raise them” – making them less likely later to fall into crime.

Children exposed to lead are more likely have behavioural difficulties and, when they become adults, to commit crimes, according to research. In the United States, lead was phased out of petrol between 1975 and 1985. Two decades later, it was found the sharpest drop in violent crime occurred in the states that were the first to reduce lead levels.

In Australia the phase-out didn’t start until 1986, but happened at the same time nationwide. “If we assume that the impact on crime was similar in both countries, it suggests that unleaded petrol might have been responsible for reductions in crime as late as the mid-2000s.”

Turning to the field of sport, Leigh declares that perhaps the biggest piece of luck you can have is to be born in the right month of the year. To make the case, he has looked at the birthdays of the general population in the 1980s and those of samples of top cricket, rugby league and soccer players, along with the age cut-off that applied to most of them when they were children.

There is little difference in the general population between the proportion born in the least and most common months for births (February and March respectively).

But for cricket, NRL and soccer, there are spikes just after the cut-off date. “This shows an excess of players who would have been among the oldest in their teams when playing age-graded sports.

"In cricket, the most common birth month is November (the third month after the cut-off), while in league and soccer the most common birth month for elite players is the month directly after the cut-off. A boy born in January is nearly twice as likely to play first-grade rugby league as a boy born in December. A boy or girl born in August is more than twice as likely to play soccer for Australia than a child born in July.”

Also, when the youth soccer cut-off point was changed (until the late 1980s it was January 1), the birth dates began to change. “If you look at the distribution of top soccer players’ birthdays in that era, the most common season of birth is the first few months of the year. But when the cut-off date was shifted, the birthdates of top soccer players began shifting too. It’s a fair bet that if we hadn’t changed the cut-off age for youth soccer, the Matildas and the Socceroos would contain more members with January birthdays and fewer members with August birthdays.”

Strangest of all are the death statistics on either side of July 1, 1979, the day federal inheritance taxes were abolished.

Leigh (building in the odd assumption) estimates that about half of those who would have paid inheritance taxes if they’d died in June “managed to shift their date of death to July”.

“How do people shift their date of death? One possibility is that families were considering whether to turn off life support. Another is that through force of will, people were able to hang on for another week. It’s also possible descendants misreported the date of death to the authorities … we can’t be sure precisely how so many people managed to avoid inheritance taxes in the final week: we just know that they did it.”

At the end, this flouts the observation about death and taxes being the two givens in life.

Become a friend of The Conversation with a tax-deductible contribution today.