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Your Friends Are Making You Fat and Lazy

This is the simple punchline of the blog of NY Times "Economix - Explaining the Science of Everyday Life" on research on peer effects in the US Air Force Academy by UC Davis economist Scott Carrell and his coauthors. The entire working paper can be downloaded here.

The authors write in the abstract "(t)he increase in obesity over the past thirty years has led researchers to investigate the role of social networks as a contributing factor. However, several challenges make it difficult to demonstrate a causal link between friends’ physical fitness and own fitness using observational data. To overcome these problems, we exploit data from a unique setting in which individuals are randomly assigned to peer groups. We find statistically significant peer effects that are 40 to 70 percent as large as the own effect of prior fitness scores on current fitness outcomes. Evidence suggests that the effects are caused primarily by friends who were the least fit, thus supporting the provocative notion that poor physical fitness spreads on a person-to-person basis."