Working Paper: NBER ID: w16518
Authors: Scott E. Carrell; Mark Hoekstra; James E. West
Abstract: The 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.
Keywords: peer effects; physical fitness; obesity; social networks; random assignment
JEL Codes: I18; I2; Z13
Edges that are evidenced by causal inference methods are in orange, and the rest are in light blue.
| Cause | Effect |
|---|---|
| poor physical fitness spreads through social networks (I14) | individual college fitness score (D29) |
| average high school fitness score of peers (I24) | individual college fitness score (D29) |
| individual's own high school fitness score (I24) | individual college fitness score (D29) |
| least fit friends (Y80) | individual college fitness score (D29) |
| peer fitness (C92) | probability of failing fitness requirements (C46) |