"In closing, however, it would be useful to pull back from issues of measurement and identification and ask more generally why a cohort effect associated with legalized abortion was not more evident in the data. I have two explanations. First, the actual number of unintended births averted, although signicant, was an order of magnitude less than the number of reported legal abortions in the early 1970s. Many analysts, including Donohue and Levitt treat reported abortions as an appropriate counterfactual for unintended childbearing. I have questioned this strategy because the availability of legal abortion may figure into decisions regarding sex and contraception, which weakens the link between abortion and fertility. Second, analysts, I being one, have tended to overestimate the selection effects associated with abortion. A careful examination of studies of pregnancy resolution reveals that women who abort are at lower risk of having children with criminal propensities than women of similar age, race and marital status who instead carried to term. For instance, in an early study of teens in Ventura County, California between 1972 and 1974, researchers demonstrated that pregnant teens with better grades, more completed schooling, and not on public assistance were much more likely to abort than their poorer, less academically oriented counterparts (Leibowitz, Eisen, and Chow 1986). Studies based on data from the National Health and Social Life Survey (NHSLS) and the National Longitudinal Survey of Youth (NLSY) make the same point (Michael 2000; Hotz, McElroy, and Sanders 1999). Indeed, Hotz, McElroy, and Sanders (1999) found that teens who abort are similar along observed characteristics to teens that were never pregnant, both of whom differ significantly from pregnant teens that spontaneously abort or carry to term. Nor is favorable selection limited to teens. Unmarried women that abort have more completed schooling and higher AFQT scores than their counterparts that carry the pregnancy to term (Powell-Griner and Trent 1987; Currie, Nixon, and Cole 1995). In sum, legalized abortion has improved the lives of many women by allowing them to avoid an unwanted birth. I found little evidence to suggest, however, that the legalization of abortion had an appreciable effect on the criminality of subsequent cohorts."