Was it really necessary to do a voting experiment on 300,000 people? Maybe 299,999 would’ve been enough? Or 299,998? Or maybe 2000?

There’s been some discussion recently about an experiment done in Montana, New Hampshire, and California, conducted by three young political science professors, in which letters were sent to 300,000 people, in order to (possibly) affect their voting behavior. It appears … Continue reading

Evidence that, in India, girls get less mother’s milk than boys, leading to higher infant mortality among girls (leaving me confused about whether this is explaining 14% or most of the differences observed in data)

Chris Blattman reports on a study by Seema Jayachandran and Ilyana Kuziemko that makes the following argument: Medical research indicates that breastfeeding suppresses post-natal fertility. We [Jayachandran and Kuziemko] model the implications for breastfeeding decisions and test the model’s predictions … Continue reading

Choices in how to write about regression results (example of an analysis of U.S. military aid in Colombia)

John reports on an article by Oeindrila Dube and Suresh Naidu, who ran some regressions on observational data and wrote:

This paper examines the effect of U.S. military aid on political violence and democracy in Colombia. We take advantage of the fact that U.S. military aid is channeled to Colombian army brigades operating out of military bases, and compare how changes in aid affect outcomes in municipalities with and without bases. Using detailed data on violence perpetuated by illegal armed groups, we …find that U.S. military aid leads to differential increases in attacks by paramilitaries . . .

It’s an interesting analysis, but I wish they’d restrained themselves and replaced all their causal language with “is associated with” and the like.

From a statistical point of view, what Dubey and Naiduz are doing is estimating the effects of military aid in two ways: first, by comparing outcomes in years in which the U.S. spends more or less in military aid; second, by comparing outcomes in cities in Colombia with and without military bases. Continue reading