Police Crackdowns: Initial and Residual Deterrence

Police crackdowns are sudden increases in officer presence, sanctions, and threats of apprehension either for specific offenses or for all offenses in specific places. Of eighteen case studies of crackdowns, fifteen appeared to demonstrate initial deterrent effects, including two examples of long-term effects. In most long-term crackdowns with apparent initial deterrence, however, the effects began to decay after a short period, sometimes despite continued dosage of police presence or even increased dosage of police sanctions. However, five studies with postcrackdown data showed a "free bonus" of continued deterrence well after the crackdowns ended. Such "residual" deterrent effects lasted in two cases for a longer period than the crackdown itself. These findings of initial decay and residual deterrence suggest that crackdowns might be more effective if they were limited in duration and rotated across different targets. While such a policy raises certain ethical and legal questions, these should not preclude a program of experimental research to establish the residual deterrent effects of short crackdowns across a range of police tactics, offense types, and places.