  To assess racial disparities in police interactions with the public, we
compiled and analyzed a dataset detailing over 60 million state patrol stops
conducted in 20 U.S. states between 2011 and 2015. We find that black drivers
are stopped more often than white drivers relative to their share of the
driving-age population, but that Hispanic drivers are stopped less often than
whites. Among stopped drivers -- and after controlling for age, gender, time,
and location -- blacks and Hispanics are more likely to be ticketed, searched,
and arrested than white drivers. These disparities may reflect differences in
driving behavior, and are not necessarily the result of bias. In the case of
search decisions, we explicitly test for discrimination by examining both the
rate at which drivers are searched and the likelihood searches turn up
contraband. We find evidence that the bar for searching black and Hispanic
drivers is lower than for searching whites. Finally, we find that legalizing
recreational marijuana in Washington and Colorado reduced the total number of
searches and misdemeanors for all race groups, though a race gap still
persists. We conclude by offering recommendations for improving data
collection, analysis, and reporting by law enforcement agencies.
