Sunday, 6 October 2013

Reduction In Crime: A Casual Link That No One Was Expecting


I was watching The Culture Show Malcolm Gladwell special on BBC2 the other day, and something struck me as strange. Jon Ronson and Malcolm Gladwell were discussing Gladwell's well known chapter in his best-selling book The Tipping Point: How Little Things Can Make a Big Difference, in which he had argued that the steep drop in the New York City crime rate after 1990 was primarily down to Mayor Giuliani's "zero-tolerance" policies. 

Ronson and Gladwell sat and deliberated over the strength of the causal link between Giuliani's "zero-tolerance" policies and the crime drop, with it being suggested by Ronson (and another contributor independently) that the causal link may not be as conclusive as Gladwell had propounded in his book. Gladwell responded with the admission that perhaps he might (stress 'might') have overestimated the causal link.

Here's what I found very strange about the whole encounter; it is very well known by readers of this particular type of modern social commentary literature that Mayor Giuliani's "zero-tolerance" policies were not the cause of the steep drop in the New York City crime rate after 1990. The cause was something quite startling - and I'm certain that Gladwell (and probably Ronson) would not have been unaware of what it is, as it was made known rather (in)famously in the excellent book Freakonomics by Steven D. Levitt and Stephen J. Dubner.

Can you guess what it was?
What Levitt and Dubner showed in Freakonomics is that it was legalisation of abortion in America that went on to have the biggest significance in reducing crime rates 15-20 years henceforward in the States in which it happened. Before 1973 abortion was illegal in all States in the America - but later in 1973 there was a court case (Roe vs. Wade), whereby (to cut a long story short) the consequent results of the judicial legal case yielded (soon after) the legalisation of abortion in about 5 states. This has fairly conclusively shown that there is cross-correlation, and that the legalisation of abortion was the single greatest cause of decrease in property crime, violent crime and murder.

In case you haven't worked out why - it's because the future criminals were no longer being born, they were being aborted.  Yes it's true, you did read me aright - legalising abortion meant that future criminals weren't being born, hence the drop in crime 18 to 24 years later. It was 18 to 24 because that is the peak of human crime life, so of course it followed that the cumulative age distribution curve for property crime, violent crime and murder matched the curves for the drops in rates of crime for these three offences in the five states, which is about as conclusive a pattern as you could wish to see.

I'm only telling you facts - of course, t
hat’s not an argument in favour of or against legalising abortion, nor does it involve any ethical judgements about abortion – it simply shows that good can come from bad, and why the moral worth of an action should not be determined by its resulting outcome, even though positive knock on effects occur where they are at the time unexpected. Furthermore, these weren't trivial drops in crime either; murder dropped by about 40%, and violent crime by about 35%.

It is not surprising that Malcolm Gladwell made the error of judgement in linking Giuliani's policies to the steep drop in crime - after all, two well known factors in crime reduction are an improved economic situation, and better policing coupled with more people in prisons (sometimes changes in law have an effect too, but most petty crime stats are fixed anyway, so one usually offsets the other). But once the rate of crime falling was known, it should have been more obvious that neither improved economic situation nor better policing were the catalysts for this reduction, because improved economic situations and better policing are highly unlikely to reduce crime by as much as 35-40% - it would take something much more significant.  Another compelling reason why decrease in crime cannot be explained by the improving economic situation of the time was that further studies showed that different economic progress in different areas did not cross-correlate with reduction in crime in those states. And better policing coupled with more people in prisons could not be the reason for the reduction in crime either, because, as before, not all places changed their policing or prison strategy, and changes were seen in many areas where there was no substantial reduction in crime.

What made the case all but conclusive was that the States of New York, Washington, Alaska and Hawaii all made abortion available three years earlier that the rest of the other States in the America. As a result, in ALL of these States, the downfall in crime rates started three years earlier than the other States. Additionally, the decrease in crime was most pronounced in the States that saw the greatest increase in the number of abortions.  All of these things lead to a pretty watertight case which shows the causal link to be very difficult to deny.

I've no idea why Ronson and Gladwell's conversation was devoid of the well known fact that legalising abortion was the primary cause in a future crime reduction (I say 'primary' because although legalising abortion wasn't the 'only' factor in the future crime reduction, it was the most significant factor). I know that Malcolm Gladwell questioned Levitt and Dubner's findings on the basis that the pill was introduced in the 1960s, and that that didn't seem to bring about future crime reduction, despite also being responsible for a lot of future people not being born. But it seems clear to me why this is likely to be the case, and why the pill did not have the same future effect as abortions. Quite simply, in all likelihood, the set that contained the kind of people who were taking the pill was a set that contained fewer people likely to produce future criminals than the set that contained people having abortions. This is backed up by numerous studies showing the link between family environment and criminality - that the demographic in which folk were more likely to have abortions (under-educated teenagers, those from broken homes, those from decadent provenances with poor social mobility, those in poverty, those dependent on welfare, those into petty crime, those that have drug or alcohol problems, and those that belong to gangs) - amounts to the same demographic in which there were folk from poor families, folk that are raised by single parents, teenage parents, uneducated parents and/or parents with drug/alcohol problems, and thus most likely to be future criminals.

Showing the causal link between legalisation of abortion and crime reduction stands as a good example of how one must never make precipitous assumptions about seemingly 'clear cut' causal links. Just about everyone thought that zero tolerance was responsible for the crime reduction - but as the studies documented in Freakonomics show - you just never know what's going to come out of the evidential woodwork.

* Photo courtesy of BBCiplayer

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