  In New York City, neighborhood policing was adopted at the police precinct
level over the years 2015-2018, and it is of interest to both (1) evaluate the
impact of the policy, and (2) understand what types of communities are most
impacted by the policy, raising questions of heterogeneous treatment effects.
We develop novel statistical approaches that are robust to unmeasured
confounding bias to study the causal effect of policies implemented at the
community level. We find that neighborhood policing decreases discretionary
arrests in certain areas of the city, but has little effect on crime or racial
disparities in arrest rates.
