The effect of legalized abortion on crime (also the Donohue–Levitt hypothesis) is a controversial hypothesis about the reduction in crime in the decades following the legalization of abortion. Proponents argue that the availability of abortion resulted in fewer births of children at the highest risk of committing crime. The earliest research suggesting such an effect was a 1966 study in Sweden. In 2001, Steven Levitt of the University of Chicago and John Donohue of Yale University argued, citing their research and earlier studies, that children who are unwanted or whose parents cannot support them are likelier to become criminals. This idea was further popularized by its inclusion in the book Freakonomics, which Levitt co-wrote. Critics have argued that Donohue and Levitt's methodologies are flawed and that no statistically significant relationship between abortion and later crime rates can be proven. Criticisms include the assumption in the Donohue-Levitt study that abortion rates increased substantially since the 1973 Supreme Court case Roe v. Wade; critics use census data to show that the changes in the overall abortion rate could not account for the decrease in crime claimed by the study's methodology (legal abortions had been permitted under limited circumstances in many states prior). Other critics state that the correlations between births and crime found by Donohue–Levitt do not adequately account for confounding factors such as reduced drug use, changes in demographics and population densities, or other contemporary cultural changes. 1972 Rockefeller Commission 12.16 The 1972 Rockefeller Commission on "Population and the American Future" cites a 1966 study which found that children born to women who had been denied an abortion "turned out to have been registered more often with psychiatric services, engaged in more antisocial and criminal behavior, and have been more dependent on public assistance." In particular, the study looked at the children of 188 women who were denied abortions from 1939 to 1941 at the hospital in Gothenburg, Sweden. They compared these unwanted children to another group – the next child born after each of the unwanted children at the hospital. The unwanted children were more likely to grow up in adverse conditions, such as having divorced parents or being raised in foster homes and were more likely to become delinquents and engaged in crime. 2001 Donohue and Levitt study Steven Levitt of the University of Chicago and John Donohue of Yale University revived discussion of this claim with their 2001