Indeed, the very localized and place-based patterns of policing are strong possible explanations of racial difference. With housing substantially segregated by race (see Sharkey 2013), a simple cause of racial difference in contact with the police could simply be that the police patrol more intensively on one side of town than the other. Naturally, the police go where the crime is, whether by design or by responding to calls for service. And this may bring them into contact with minorities with greater frequency than whites.
