Estimating Deterrence Effects Using Random Crackdowns: Theory and Evidence∗

This paper develops a theory of policing that can explain the phenomenon of random “crackdowns, ” which are periods of especially high interdiction/surveillance that are announced ahead of time and are sustained temporarily. We show that, when police minimize the crime rate, random crackdowns can emerge as part of an optimal policing strategy. These crackdowns provide a way of estimating the deterrence effect of policing that does not rely on exogenous variation in police resources. We consider alternative specifications of police objective functions and show that crackdowns would not arise if police activities are decentralized. We demonstrate support for several implications of the crackdown theory using traffic data gathered by the Police Department in Belgium, and we use the model to estimate the deterrence effect of policing on speeding. ∗This paper was improved by comments received at the April 2003 University of Pennsylvania IER crime conference, at the October 2003 Northwestern NSF conference on profiling, and at seminars a