Abortion rate and crime rate could be related, but I don't think it is a direct correlation. You have to consider that the "lower rungs of society" who are most likely to produce tomorrows criminals don't always have access to abortion techniques. I think the real thing that has lowered crime rate is birth control.
Statistics never reveal the true picture. Instead of those from lower socio- economic backgrounds should have the child and let it be brought up by more parenting able people that way lives would be saved there would be less crime and there wouldnt be so much of an ageing population
Levitt is a brilliant economist; arguably one of the best in the world. His unorthodox approach to economics (focusing on the economic impact of social issues) has been a great contribution to public policy. He never makes theories based solely on correlations. I would assume that he has solid empirical data and theoretical basic to support his views.