June 22, 2006

Dills & Miron on Levitt's latest defense of his abortion-cut-crime theory

Another nail in the coffin of the Freakonomics theory that abortion cut crime: When I pointed out to Steven D. Levitt in 1999 that not only did crime not drop among the first cohort born after the legalization of abortion, but that the age 14-17 homicide rate hit its historic peak in 1993-94, his defense was, in effect, well, okay, but that's only at the national level. If you had run a massive econometric study at the state level, like I did, you'd see my theory is validated.

Last fall, economists Christopher Foote and Christopher Goetz finally reran Levitt and Donohue's original state-level analysis and found Levitt had made two fatal technical mistakes. When those flubs were corrected, his entire claimed effect disappeared. (Of course, by then, Freakonomics was the publishing sensation of the year and Levitt had signed deals with ABC and the New York Times, so he cried all the way to the bank.)

Levitt & Donohue's response was to present a new data set, which they claimed validated their original theory.

Now, two economists have analyzed their new data and here's the beginning and the end of their brief paper:

A Comment on Donohue and Levitt's (2006) Reply to Foote and Goetz (2005)

Angela K. Dills Department of Economics, Clemson University
Jeffrey A. Miron Visiting Professor of Economics, Harvard University April, 2006

Donohue and Levitt (2001) (DLI) consider the hypothesis that U.S. legalization of abortion in the early 1970s caused much of the decline in crime in the 1990s. Foote and Goetz (2006) (FG) show, however, that one key result in DLI contained a coding error; dummies for state-year interactions were inadvertently omitted from the regressions. FG demonstrate that correcting this error, along with estimating the regressions using arrest rates rather than arrest levels, suggests virtually no effect of legalized abortion on crime.

Donohue and Levitt (2006) (DLII) acknowledge the coding error and agree that correcting the mistake and using arrest rates suggests no effect of legalized abortion on crime. DLII argue, however, that use of an improved abortion measure and an instrumental variable revives or even strengthens their original result...

Our conclusion is that the kind of analysis considered in Table VII of DLII does not suggest a quantitatively important effect of legalized abortion on crime. The best case for such an effect is the IV results in columns (6) and (7); these imply that abortion legalization explain 24-25.9% of the 1991-1998 decline in violent crime and 7.1-8.1% of that in property crime. None of these coefficients is statistically significant at conventional levels, however, and the results in column (8) suggest they rely on an implausible mechanism relating abortion to crime. [Full Length PDF]

Large assertions require large proof, and after seven years, Levitt hasn't come close to meeting the burden of proof.

My published articles are archived at iSteve.com -- Steve Sailer

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