Endogenous Driving Behavior in Tests of Racial Profiling

African-American motorists may adjust their behavior in response to increased scrutiny by police, biasing tests of discrimination that rely on the share of treated individuals who are minority, such as for traffic stops. We use the “veil of darkness” strategy to examine traffic fatalities and speeding infractions to detect such behavioral responses. In daylight, when race is more easily observable, African-American motorists are less likely to have fatal motor vehicle accidents. In Massachusetts and Tennessee, we find that stopped African-American motorists drove at slower speeds in daylight. Calibrations indicate that this behavior creates substantial bias in conventional tests of discrimination.