A quasi-experimental synthetic control evaluation of a place-based police-directed patrol intervention on violent crime
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Date
2/8/2018
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Experimental Criminology
Abstract
This research evaluates the impact of an implementation of a place-based police-directed patrol intervention—originally based on the Data Driven Approaches to Crime and Traffic Safety (DDACTS) model—on violent crime in Flint, Michigan, USA. Methods We utilize recent advances in synthetic control methods to implement a retrospective quasi-experimental design across seven separate intervention areas, producing a counterfactual estimate of what would have happened to violent crime had the intervention never been implemented. We use survey weight calibration to produce counterfactual intervention areas using comparison block groups in Flint, and account for treatment diffusion by using comparison block groups from Detroit. Results The synthetic control method calibrated a set of weights to exactly match the intervention hot spots to counterfactuals from Flint and Detroit. Although basic trend analyses suggested declines in violent crime in the treatment areas, the synthetic controls raised questions about treatment effects. Specifically, the Flint comparison revealed an unexpected increase in aggravated assaults associated with the intervention, whereas the Detroit comparison suggested a similar effect but also possible reduction in robberies.
Description
Objectives
This research evaluates the impact of an implementation of a place-based police-directed patrol intervention—originally based on the Data Driven Approaches to Crime and Traffic Safety (DDACTS) model—on violent crime in Flint, Michigan, USA.
Methods
We utilize recent advances in synthetic control methods to implement a retrospective quasi-experimental design across seven separate intervention areas, producing a counterfactual estimate of what would have happened to violent crime had the intervention never been implemented. We use survey weight calibration to produce counterfactual intervention areas using comparison block groups in Flint, and account for treatment diffusion by using comparison block groups from Detroit.
Results
The synthetic control method calibrated a set of weights to exactly match the intervention hot spots to counterfactuals from Flint and Detroit. Although basic trend analyses suggested declines in violent crime in the treatment areas, the synthetic controls raised questions about treatment effects. Specifically, the Flint comparison revealed an unexpected increase in aggravated assaults associated with the intervention, whereas the Detroit comparison suggested a similar effect but also possible reduction in robberies.