I have not yet read Freakonomics, but I have heard good things about the book from friends. Apparently one chapter within the book discusses the effect of correlation between the legalization of abortion in the 1970s on and the amount of crime in the 1990s.
An article in the Wall Street Journal [free] explains the premise:
Unwanted children are more likely to become troubled adolescents, prone to crime and drug use, than are wanted children. When abortion was legalized in the 1970s, a whole generation of unwanted births were averted, leading to a drop in crime nearly two decades later when this phantom generation would have come of age.
The article then disputes, or cites other economists who dispute, the statistics gathered in the study
The Boston Fed’s Mr. Foote says he spotted a missing formula in the programming of Mr. Levitt’s original research. He argues the programming oversight made it difficult to pick up other factors that might have influenced crime rates during the 1980s and 1990s, like the crack wave that waxed and waned during that period.
The authors of Freakonomics are on the defense and have struck back on their blog with a preliminary response.
This is where I like to say there’s a certain percentage of statistics that are made up. Let’s say 97%. I’m not claiming that Steven D. Levitt and Stephen J. Dubner invented numbers to support their theory, and the WSJ article doesn’t contain enough information to debunk their entire research on the subject. I’ll be interested in seeing how the disagreement plays out.
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8:50 pm (reply)
I guess I’d be interested to know how they think they were able to keep all the other influences on crime out of their hypothesis. At first glance, it sure seems like there is another agenda behind their statements, but then again, I’m just an amateur financial blogger. Both subjects, (crime and abortion) are pretty intense subjects and I’ve never heard anyone try to draw a correlation between them. It just seems like there are too many other variables that could be at play.
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11:11 pm (reply)
It’s been awhile since I read the book, but I don’t think Levitt really tried to draw solid cause and effect relationships. He simply noted some interesting correlations.
The book was a fun read however I was really expecting more technical information than it presented.
1:32 pm (reply)
If you actually read the book, you will see that the authors make an concerted effort to point out the difference between correlation and causation. Their sources are obviously in the back of the book and available for anyone who wants more info.
1:39 pm (reply)
I’m glad to hear they make that distinction. I tend to harp on the necessity of making that clear. Correlation doesn’t imply causation, and that fact is often lost on people who misunderstand statistics.
It seems, judging by the comments on the Freakonomics blog, that the detractors are disputing the correlation, and not an unasserted causation, despite my use of the word “effect” above and the first sentence of the quote from the Wall Street Journal’s article.