Freakonomics: Crime

I haven't seen the movie Freakonomics, but something in a review caught my eye: the claim that dropping crime rates in the US are due primarily to the Roe v. Wade decision of 1973. Here's how Kenneth Turan of the Los Angeles Times describes it:

Much more counterintuitive is Jarecki's "It's (Not Always) a Wonderful Life." The subject here is a favorite of pundits: speculating on what caused the much-written-about drop in crime rates in the 1990s.Using animation and clips from the James Stewart classic, Jarecki illustrates Dubner's theory by first bringing up and dismissing the most conventional theories about the source of the decline: innovative policing techniques, harsher prison sentences, changes in the habits of drug users. Instead, the economist advances the notion that it was the Supreme Court's 1973 Roe vs. Wade decision, which legalized abortion and thereby reduced the number of babies with two strong indicators of a criminal future — being poor and being raised by a single parent — which caused crime to drop. Now that's freakonomics in a nutshell.I talk about the issue of crime (actually gun homicide rates) in my Foundations of Comparative Politics in the context of using comparative methodology to study real-world social, political or economic issues. Since I have not seen the actual argument--and it does seem intriguing (something on my "to see" list)--my comments will be circumspect. This said, the description above seems to boil the issue of crime down to a single factor, which is exceedingly problematic, albeit not necessarily wrong.

To test the claim appropriately, the researchers would not only need to be able to control for a range of other factors (innovative and more effective policing techniques, harsher prison terms, the "three strikes" law, etc.), but also demonstrate that these factors did not contribute to the reduction of crime in any meaningful way. In this regard, we also have to understand that, even if the Roe v. Wade decision had a material effect, its effect may have been significantly amplified--perhaps critically so--by the existence of other changes that have occurred since 1973. This is referred to as complex causality. Practically speaking, however, this cannot be done since those other factors cannot be adequately controlled for. Now, if the US were to revoke Roe v. Wade, and if no other material changes occurred, we would have a perfect scenario for a "testing" the Freakonomics claim--in other words, we would be able to conduct a within-case comparison in which we could control for a range of relevant variables while isolating the effects of "limited abortion."