In this paper, the authors provide an assessment of a parolee-based focused deterrence intervention, aimed at mitigating community-level violence including firearm and non-firearm violence; the paper includes an appendix with data for comparison cities used for counterfactual creation and posterior inclusion probabilities.
The authors estimate the impact of a parolee-based focused deterrence (“pulling levers”) intervention on community-level firearm and non-firearm violence in Rockford, Illinois, via a retrospective, quasi-experimental design. Focusing on incidents of firearm violence in Rockford over a period of 60 months, with 38 months pre-intervention and 22 months post-intervention, the authors assess program impact by using Bayesian Structural Time Series (BSTS) models, constructing a synthetic control-based counterfactual time series from National Incident-Based Reporting System (NIBRS) data from 59 non-treated cities of similar size. Relative to the synthetic control counterfactual, the intervention was associated with significant reductions in both firearm and non-firearm violence, particularly robberies, ranging from six percent to 30 percent. Consistent with research at other sites, these findings support the notion that focused deterrence strategies centered on high-risk parolees may result in reductions in firearm violence at the community level. The BSTS approach is a useful application for producing counterfactuals in retrospective quasi-experimental impact evaluations. Publisher Abstract Provided