Sanctuary Policies and City-Level Incidents of Violence, 1990 to 2010

Despite media coverage of isolated incidents of violent crime perpetuated by undocumented immigrants in cities with sanctuary policies, there is scant systematic research on the relationships between the adoption of sanctuary policies, unauthorized immigration, and crime. We compile city-level data from official sources and use fixed-effects negative binomial regression to examine whether the adoption of city-level sanctuary policies and the concentration of unauthorized Mexican immigrants are associated with homicide and robbery incidents in 107 U.S. cities, across three decades. We find evidence that the adoption of sanctuary policies is associated with a reduction in robberies but not homicide. In contrast, an increase in the relative size of a city’s unauthorized Mexican immigrant population corresponds with a reduction in homicide; however, only in sanctuary cities. Lastly, shifts in violence during our study period are consistently related to social structural characteristics of cities, which are findings consistent with social disorganization theory.