Displacement Effects in a Hot Spot Policing Intervention in Medellin: Inference and Pitfalls

Guillaume Basse
Stanford University

Wednesday, Nov 18, 2020
8:30 - 9:30 AM


In hot spot policing, resources are targeted at specific locations predicted to be at high risk of crime; so-called ``hot spots.'' Rather than reduce overall crime, however, there is a concern that these interventions simply displace crime from the targeted locations to nearby non-hot spots. We address this question in the context of a large-scale randomized experiment in Medellin, Colombia, in which police were randomly assigned to increase patrols at a subset of possible hotspots. Estimating the displacement effects on control locations is difficult because the probability that a nearby hotspot is treated is a complex function of the underlying geography. While existing methods developed for this ``general interference'' setting, especially Horvitz-Thompson (HT) estimators, have attractive theoretical properties, they can perform poorly in practice and mislead practitioners. In this talk, I explore the key pitfalls that practitioners should watch out for when conducting this type of analysis, and propose some ways to partially remedy them.

Operations Research Colloquia: http://or.stanford.edu/oras_seminars.html