Police officer on the frontline or a soldier? The effect of police militarization on crime

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.