Wednesday, December 11, 2013

Meta-analysis of the elasticity of intertemporal substitution

The elasticity of intertemporal substitution is one of the most estimated parameters in Economics. Why is it estimated over and over again? Because some results are positive, some are negative and some are zero. To have a clearer idea of what its true value is, we have to keep estimating it. However, the econometricians also need to get their results published, and the publishing tournament has not only an impact on which results get published but also on which ones the econometricians submit for publication.

Tomáš Havránek performs a meta-analysis of estimates of the elasticity of intertemporal substitution. That is, he gathers 169 studies and looks at their 2735 estimates. He finds significant under-reporting of results close to zero or negative, because of this publication bias. While the published mean is 0.5, the true mean should somewhere at 0.3 to 0.4. Negative results make little sense, but they can happen with some draw of the data. If editors and referees systematically discard such results, and positive ones, no matter how large they are, get a pass, we have a bias. But given the distribution of published ones, and knowing this bias, one can infer the full distribution of estimates, and hence Havránek's new estimates.

No comments: