Effects of Police Gun Suppression Patrols on Shots Fired and Gunshot Injuries: Estimating Impacts of Naturally Occurring Interventions

Jacqueline Cohen, Carnegie Mellon University

The surge of youth violence in the late 1980s was in part the result of an increase in illicit carrying of guns by youths on public streets. Often with funding from external sources, police in U.S. cities partnered with research teams and local communities to design, implement and evaluate proactive enforcement strategies aimed at reducing gun violence. In several cities, these strategies involved enhanced police resources to vigorously patrol targeted high-risk neighborhoods seeking to locate and seize illegal firearms. Increased police contacts through vehicle stops, investigations of disorderly behavior, and other field contacts were intended to provide opportunities for identifying persons illegally carrying firearms. This paper reports the results of one such effort in Pittsburgh. Like other similar studies, the special gun suppression patrols in Pittsburgh were accompanied by significant reductions in illegal gun activities. Emergency 911 calls reporting shots fired declined by more than 50% in one target area, and gunshot injuries were down by nearly 70% in another. The unique contributions of the present study include novel application of a repeated-differencing method that provides improved statistical controls for non-experimental differences between naturally occurring target and comparison areas. The analysis also uses novel outcome measures that are more directly related to illegal gun activities and not subject to organizational filtering by police. Finally, the results indicate that substantial reductions in gun violence can be achieved even at relatively low expenditures of police resources.

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Updated 05/20/2006