Effects of abortion ban
There have been many responses to the theory that legal abortion reduces crime – see Legalized abortion and crime effect: Responses and The Impact of Legalized Abortion on Crime for details.
Freakonomics commented on the effects of an abortion ban in Romania (Decree 770), stating that "Compared to Romanian children born just a year earlier, the cohort of children born after the abortion ban would do worse in every measurable way: they would test lower in school, they would have less success in the labor market, and they would also prove much more likely to become criminals. (p. 118)". John DiNardo, a professor at the University of Michigan, retorts that the paper cited by Freakonomics states "virtually the opposite of what is actually claimed":
On average, children born in 1967 just after abortions became illegal display better educational and labor market achievements than children born prior to the change. This outcome can be explained by a change in the composition of women having children: urban, educated women were more likely to have abortions prior to the policy change, so a higher proportion of children were born into urban, educated households. (Pop-Eleches, 2002, p.34).—John DiNardo, Freakonomics: Scholarship in the Service of Storytelling
Levitt responded on the Freakonomics Blog that Freakonomics and Pop-Eleches "are saying the same thing":
Here is the abstract of the version of the Pop-Eleches paper that we cited:
…Children born after the abortion ban attained more years of schooling and greater labor market success. This is because urban, educated women were more likely to have abortions prior to the policy change, and the relative number of children born to this type of woman increased after the ban. However, controlling for composition using observable background variables, children born after the ban on abortions had worse educational and labor market achievements as adults. Additionally, I provide evidence of crowding in the school system and some suggestive evidence that cohorts born after the introduction of the abortion ban had higher infant mortality and increased criminal behavior later in life.
The introduction of the Pop-Eleches paper says:
This finding is consistent with the view that children who were unwanted during pregnancy had worse socio-economic outcomes once they became adults.
Effects of extra police on crime
Freakonomics claimed that it was possible to "tease" out the effect of extra police on crime by analysing electoral cycles. The evidence behind these claims was shown to be due partly to a programming error. McCrary stated "While municipal police force size does appear to vary over state and local electoral cycles ... elections do not induce enough variation in police hiring to generate informative estimates of the effect of police on crime."