Effect of Gang Injunctions on Crime: A Study of Los Angeles from 1988-2014

Objective To assess the effect of civil gang injunctions on crime. Methods We use data on the location and date of 46 gang injunctions between 1993 and 2013 and quarterly crimes reported to the Los Angeles Police Department (LAPD) from 1988 to 2014. We estimate the effect of gang injunctions on crime over the short-term (20 quarters) and long-term (108 quarters) using difference-in-differences designs that take into account spatial and temporal correlation. Three gang injunctions were paused during the study period and provide a natural experiment from which we estimate the short-term effect of these injunctions on crime. Results Gang injunctions are estimated to reduce total crime 5% in the short-term and 18% in the long-term, most of the effect coming from reductions in assaults. Analyses of the three interrupted injunctions yielded estimates of similar magnitude, providing further support of a crime reduction effect of gang injunctions. We found no evidence that gang injunctions are associated with displacing crime to nearby areas. Conclusions Injunctions represent a powerful place-based intervention strategy for police and prosecutors. Courts have recently subjected gang injunctions to closer scrutiny. This study indicates that gang injunctions contributed to a meaningful amount of the crime reductions in Los Angeles. Future research should examine whether gang injunctions reduce crime by specific deterrent effects on individual gang members or by the general deterrent effect of placing an area under greater police surveillance and restricting public gatherings and other actions deemed to be indicators of gang activity.