Why economists need epidemiologists

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Tim Harford says that Emily Oster’s work on AIDS has serious flaws:

One of her celebrated articles is an analysis of the Aids epidemic in Africa: she offers her own epidemiological model and concludes that the virus is best fought by treating other sexually transmitted diseases. The research was published in the prestigious Quarterly Journal of Economics (QJE) in May 2005.

But Oster’s conclusion is probably wrong. Epidemiologists embraced the idea of treating other sexually transmitted diseases a long time ago, but it has been discredited (to their deep disappointment) by a series of rigorous clinical trials. Oster says that the most convincing evidence came out after her paper was written; still, she has repeated her recommendations more recently in Esquire magazine.

Oster also made a mistake in handling her data. The error – which she has acknowledged, and which makes a modest but noticeable difference to her calculations – was quickly spotted when I asked two epidemiologists to review her research. The QJE will be publishing a correction.

Oster quite reasonably says that her article has other merits. But it might have been much better if the epidemiologists had taken a look long before the FT got involved.

The problem is that the economists couldn’t get the epidemiologists to take the research seriously enough to comment. Oster tells me that she tried, but she couldn’t name an epidemiologist who was familiar with her QJE paper. And Larry Katz, the QJE editor who published Oster’s paper, acknowledges that the epidemiologists would not typically agree to review papers for the QJE.

Props to Harford for his productive contributions to the research process.

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