Equal access to voting is a core feature of democratic government. Using data from hundreds of thousands of smartphone users, we quantify a racial disparity in voting wait times across a nationwide sample of polling places during the 2016 U.S. presidential election. Relative to entirely white neighborhoods, residents of entirely black neighborhoods waited 29% longer to vote and were 74% more likely to spend more than thirty minutes at their polling place. This disparity holds when comparing predominantly white and black polling places within the same states and counties and survives numerous robustness and placebo tests. We shed light on the mechanism for these results and discuss how geospatial data can be an effective tool to measure and monitor these disparities going forward.

Research on policing has focused on documented actions such as stops and arrests—less is known about patrols and presence. We map the neighborhood movement of nearly 10,000 officers across 21 of America’s largest cities using anonymized smartphone data. Police spend 0.36% more time in neighborhoods for each percentage point increase in Black residents. This neighborhood-level disparity persists after controlling for density, socioeconomic status, and crime-driven demand for policing, and may be lower in cities with more Black police supervisors (but not officers). Patterns of police presence statistically explain 57% of the higher arrest rate in more Black neighborhoods.