Donohue and Levitt revisit their famous paper on abortion and crime

As I mentioned in yesterday's book review, there was a vigorous debate back in the 2000s about this paper by John Donohue (Stanford University) and Steven Levitt (of Freakonomics fame, and the University of Chicago). So much so that the debate even has its own Wikipedia page. You can read the original paper, published in the Quarterly Journal of Economics, here (ungated version here). The short summary is that Donohue and Levitt found a link between legalising abortion in the U.S. in the 1970s, and subsequent reductions in crime in the 1990s. In fact, they concluded that legalised abortion may have accounted for 50 percent of the decrease in crime. One of the most robust arguments against their findings was this article by Christopher Foote and Christopher Goetz, also published in the Quarterly Journal of Economics (ungated version here), where they showed that using arrest rates instead of arrest totals, the effect went away (and they had other criticisms of the original paper as well).

In a new volley in this debate, Donohue and Levitt followed up on their 2001 paper last year with a new NBER Working Paper. In this new paper, they repeat the same analysis, using an additional 17 years of data. They find that their original results still hold:

The estimated coefficient on legalized abortion is actually larger in the latter period than it was in the initial dataset in almost all specifications. We estimate that crime fell roughly 20% between 1997 and 2014 due to legalized abortion. The cumulative impact of legalized abortion on crime is roughly 45%, accounting for a very substantial portion of the roughly 50-55% overall decline from the peak of crime in the early 1990s.

Here's their Figure III, which I think nicely encapsulates the key result:

The blue line tracks the difference in violent crime between 19 high-abortion states and 32 low-abortion states (District of Columbia counts as a state in their analysis, which is why there are 51), while the red line tracks the difference in effective abortion rates between high-abortion states and low-abortion states. As the difference in abortion rates increases, the difference in violent crimes decreases.

This is hardly going to be the last word in this debate though. Given that this analysis simply repeats the original analysis but with more data, expect the same objections to be raised this time around.

[HT: Marginal Revolution, last year]