ABSTRACT

Do police reduce crime? Assessing the policing effect has vexed scholars for generations. Governments may deploy police to areas with expected high crime, seriously confounding observational inference. To break the simultaneity of crime and police, one approach has been to exploit natural experiments that affect police levels in ways unrelated to expected crime. Researchers, for example, have studied electoral cycles, 2 tsunamis, 3 terror alert levels, 4 terrorist attacks, 5 and federal grants to police agencies as inducing plausibly exogenous variation in policing to credibly assess its effect. 6