Levitt's Abortion "Disappeared" When "Programming" Error Fixed

Levitt's Abortion results disappeared when programming Error Fixed

"The Boston Fed's Mr. Foote says he spotted a missing formula in the programming oversight of Mr. Levitt's original research. He argues that the programming oversight made it difficult to pick up other factors that might have influenced crime rates during the 1980s and 1990s . . . . He also argues that Levitt should have counted arrests on a per-capita basis. Instead, he coundted overall arrests. After he adjusted for both factors, Mr. Foote says, the abortion effect disappeared.

Christopher L. Foote and Christopher F. Goetz's paper can be found here. Personally, I think calling this a "programming oversight" is being much too nice (See my post here to see an example of what you would have to miss to not notice whether you have used fixed effects). More importantly everyone who works with panel data knows that you use fixed effects.

My own work concentrated on murder rates, but I also included fixed effects. Donohue and Levitt never provided us with all their data or their regressions and would never answer any questions that we had so I just assumed that they had included fixed effects from the beginning. It would have been nice if they had provided us with this same information years ago.

My paper with John Whitley is available here.
A letter that I had in the WSJ is available here.
James Q. Wilson's review of this debate is available here.


See also Steve Sailer's past work on this topic.
See also Steve Sailer's compliation of what others are saying here.

UPDATE II (I have been asked about inaccurate claims regarding my own research in More Guns, Less Crime):

See this for a discussion about claimed errors in More Guns, Less Crime

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Blogger Steve Sailer said...

Ever since I debated Dr. Levitt in Slate.com in 1999 over his abortion-cut-crime theory ( http://www.slate.com/id/33569/entry/33571/) , people have been telling me that my simpleminded little graphs and ratios of national crime trends showing that Dr. Levitt hadn’t met the burden of proof couldn’t possibly be right because Dr. Levitt’s state-level evidence was so much more gloriously, glamorously, incomprehensibly complicated than mine, and Occam’s Butterknife says that the guy with the most convoluted argument wins.

Well, now we now why Dr. Levitt’s abstruse state-level analysis didn’t match up with my straight-forward national-level analysis: because he made two big mistakes in his work.

You can see the facts that Dr. Levitt left out of Freakonomics at www.iSteve.com/abortion.htm

11/28/2005 5:36 PM  
Blogger John Lott said...

Thanks, Steve. I have added a link to your work in the primary discussion on this post. My only comment is that there were more than two major mistakes with Levitt's work. For example, in addition, it was wrong to assume that the number of legal abortions prior to legalization were zero. Also, using arrest rate data to make the breakdown of murders by age is also quite inferior to using the Supplemental Homicide Report.

11/28/2005 5:58 PM  

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