Marginal Deterrence at Work

The marginal deterrence principle of law enforcement implies that penalties must be scaled according to the severity of crimes, in order to deter individuals from committing more severe offenses. In this paper, we test whether the US legal system is consistent with the rational economic model of marginal deterrence. To this purpose, we use novel and unique data on sentence length for a large sample of inmates in US correctional facilities, combined with an official ranking of crimes by severity and with proxies for the maximum possible punishment and for the cost of monitoring criminals (specifically, the cost of policing) in each US state, over a period spanning up to 50 years. We find that sentences are on average longer in states where maximum punishment is higher and monitoring cost is lower. We document that these relations are systematically stronger in states where the private benefits from crime are more heterogeneous. Finally, we show that sanctions increase relatively faster with the severity of crimes in states with higher maximum punishment and lower monitoring cost. Overall, these results point to the rational economic model of marginal deterrence as providing a reasonable description of the actual enforcement policies chosen by regulators.