Andrew Gelman and Kaiser Fung have an article on Freakonomics in American Scientist. My favorite part was the story of Emily Oster and her theory of Hepatitis B: Monica Das Gupta is a World Bank researcher who, along with others in her field, has attributed the abnormally high ratio of boy-to-girl births in Asian countries to a preference for sons, which manifests in selective abortion and, possibly, infanticide. As a graduate student in economics, Emily Oster now a professor at the University of Chicago attacked this conventional wisdom. In an essay in Slate, Dubner and Levitt praised Oster and her study, which was published in the Journal of Political Economy during Levitt’s tenure as editor:

[Oster] measured the incidence of hepatitis B in the populations of China, India, Pakistan, Egypt, Bangladesh, and other countries where mothers gave birth to an unnaturally high number of boys. Sure enough, the regions with the most hepatitis B were the regions with the most “missing” women. Except the women weren’t really missing at all, for they had never been born.

Oster’s work stirred debate for a few years in the epidemiological literature, but eventually she admitted that the subject-matter experts had been right all along. One of Das Gupta’s many convincing counterpoints was a graph showing that in Taiwan, the ratio of boys to girls was near the natural rate for first and second babies 106:100 but not for third babies 112:100; this pattern held up with or without hepatitis B. In a follow-up blog post, Levitt applauded Oster for bravery in admitting her mistake, but he never credited Das Gupta for her superior work. Our point is not that Das Gupta had to be right and Oster wrong, but that Levitt and Dubner, in their celebration of economics and economists, suspended their critical thinking. I think that this story actually has two elements. One is the dangers of a convincing explanation. There are a lot of associations that can appear and would be extremely exciting if they were true. Just consider the recent article on statins reducing mortality due to pneumonia: it is an amazing result that would be extremely exciting if it were true.

via Observational Epidemiology: A really nice article by Andrew Gelman and Kaiser Fung.