Unexpected Effects of Roe V. Wade

[Stephen Levitt's] paper linking a rise in abortion to a drop in crime has made more noise than the rest combined. Levitt and his co-author, John Donohue of Stanford Law School, argued that as much as 50 percent of the huge drop in crime since the early 1990's can be traced to Roe v. Wade. Their thinking goes like this: the women most likely to seek an abortion -- poor, single, black or teenage mothers -- were the very women whose children, if born, have been shown most likely to become criminals. But since those children weren't born, crime began to decrease during the years they would have entered their criminal prime. In conversation, Levitt reduces the theory to a tidy syllogism: Unwantedness leads to high crime; abortion leads to less unwantedness; abortion leads to less crime.

Source: Dubner, Stephen. "The Probability That a Real-Estate Agent Is Cheating You." The New York Times 3 Aug 2003.