Legalized abortion may lead to reduced crime through any of three channels. The first channel is simply a smaller cohort size. If abortion reduces the number of births, when that cohort reaches the late teens and twenties, there will be fewer young males, and thus less crime. Abortion may also lower per capita offending rates in affected cohorts. The children may on average be less criminal due to either a ‘selective-abortion effect or an ‘improved-environment’ effect. The selective-abortion channel will operate if the women who have abortions are the most at risk to give birth to children who would engage in criminal activity. . . . The improved-environment effect may be present if women use abortion to optimize the timing of childbearing.