Surprising to me:
Sparked by high-profile confrontations between police and citizens in Ferguson, Missouri, and elsewhere, many commentators have criticized the excessive militarization of law enforcement. We investigate whether surplus military-grade equipment acquired by local police departments from the Pentagon has an effect on crime rates. We use temporal variations in US military expenditure and between-counties variation in the odds of receiving a positive amount of military aid to identify the causal effect of militarized policing on crime. We find that (i) military aid reduces street-level crime; (ii) the program is cost-effective; and (iii) there is evidence in favor of a deterrence mechanism.
--Vincenzo Bove and Evelina Gavrilova, "Police Officer on the Frontline or a Soldier? The Effect of Police Militarization on Crime," American Economic Journal: Economic Policy
We provide the first local level empirical analysis of the causal effects of providing military equipment to local police. Employing a novel combination of publicly available county-year panel data matched to hand-collected data on citizen complaints, we investigate the effects of acquiring tactical weapons, optics, and vehicles on citizen complaints, assaults on police officers, and offender deaths. For causal identification, we exploit exogenous variation in equipment availability and cost-shifting institutional aspects of the 1033 Program. Our results indicate that these items have generally positive effects: reduced citizen complaints, reduced assaults on officers, increased drug crime arrests, and no increases in offender deaths.
--Matthew Harris, Jinseong Park, Donald Bruce, and Matthew Murray, "Peacekeeping Force: Effects of Providing Tactical Equipment to Local Law Enforcement," American Economic Journal: Economic Policy