Racial disparities in law enforcement: The role of in-group bias and electoral pressures

Racial disparities are widespread throughout the U.S. justice system; in arrests and incarceration. These disparities are typically explained by appealing to racial biases among the police and the judiciary. I present a model in which disparities arise between groups in spite of unbiased actions on the part of these authorities. I assume that individuals discount the harm caused by criminal acts by members of their own group. Voters in each county determine the intensity with which legal sanctions are enforced against crimes. There are two groups, with the median voter drawn from the majority. In this model the intensity of law enforcement increases with the size of the minority. When counties are heterogeneous this leads to group disparities at the state level. The intensity of law enforcement depends on both the level of policing and the strictness of the judiciary. In some states, voters can elect their judges and increase the legal sanction through judicial severity, while in other states judges are appointed. We should therefore expect that the relationship between the size of the minority population and the intensity of policing to be stronger in counties where judges are appointed. Using a county-level panel of arrests between 2000-2014 in the United States, I find that in states with appointed judges the level of policing is increasing with the share of the black population. A 1% higher share of black population leads to a 0.58% increase in the clearance rate of property crimes. I do not find a comparable effect in states with elected judges. This agrees with the predictions of the theoretical model.