Further Evidence that Legalized Abortion Lowered Crime
回应Joyce(2003)对堕胎合法化降低犯罪率的质疑，指出其结论源于仅关注可卡因流行高峰期的偏差，通过扩展样本期至同一批人的完整生命周期，再次证实堕胎与犯罪率下降的负相关关系。
Donohue and Levitt (2001) suggest there is a causal link between legalized abortion and reductions in crime almost two decades later when the cohorts exposed to legalized abortion reach their peak crime years. Joyce (2003) examines crime committed in the period 1985–90 for the cohorts born immediately before and after abortion legalization. He finds little impact of legalized abortion. In this paper, we demonstrate that Joyce's failure to uncover a negative relationship between abortion and crime is a consequence of his decision to focus almost exclusively on one nonrepresentative six-year period during the peak of the crack epidemic. We provide empirical evidence that the crack-cocaine epidemic hit the high-abortion early-legalizing states earlier and more severely than other states. When we simply replicate his analyses, but extend the sample to cover the entire lives of these exact same cohorts, abortion is just as negatively related to crime as in our original analysis. Joyce's results appear to be purely an artifact of omitted variable bias due to focusing on the peak crack years without including adequate controls for crack.