Do Peers Matter in the Police Academy?

Increasing underrepresented groups’ representation in police departments is a common proposal to reduce aggressive policing. This paper documents the effects of peer composition in the Chicago police academy on officers’ future arrests by exploiting the lottery system, which provides exogenous variation in cohort composition. I find that higher shares of peers from groups that police less aggressively, such as female and older officers, reduce all officers’ future low-level arrests. Peer race matters by amplifying the effects of gender and age. Overall, the results are most consistent with peers’ preferences for less aggressive policing shifting officers’ preferences and changing future behavior. (JEL H76, J15, J16, J45, J78, K42)