News Release

Big data reveal threats to minorities policed by white and male officers

Peer-Reviewed Publication

American Association for the Advancement of Science (AAAS)

Using a dataset on daily patrols and enforcement activities of officers in the Chicago Police Department (CPD) - an agency that has undergone substantial diversification in recent decades - researchers report Black officers used force less often than white officers during the three-year period studied, and women used force less often than men. These and other findings provide insight into impacts of diversification in policing, a widely proposed policing reform. "The magnitude of the differences [here] provides strong evidence that--at least in some cities--the number of officers who identify with vulnerable groups can matter quite a bit in predicting police behavior," writes Philip Goff in a related Perspective. Racial disparities in police-civilian interactions and high-profile incidents of excessive force continue to fuel allegations of abusive and discriminatory policing. Diversification of police agencies at the level of race and gender is a widely proposed policing reform. But consensus is lacking on key related matters, including what influence officer demographics may hold on officer behavior. Scholars often assert such questions remain unanswered because of the scarcity of data needed for making causal inference. "As a result," Goff writes, "when scholars identify data that allow for strong inference around race and policing, they are rightly lauded by the field. And, to be sure, [the authors of this paper] should be celebrated."

Using newly acquired data on Chicago Police Department (CPD) officers' daily patrols and activities, Bocar Ba and colleagues set out to provide "the most credible microlevel evidence to date on the treatment civilians can expect when encountering officers of varied racial, ethnic and gender identifies," the authors write. In past studies, data compared officers within or between departments but could not account for where, when, or whom officers were policing. This made it challenging to ensure officers were only compared against other officers facing the same kinds of civilian behavior. To overcome this, Ba and team drew on detailed data assembled through three years of open-records requests. "This is a quantum advance for making strong inferences," says Goff. First, the authors were able to show that minority officers receive vastly different patrol assignments. From their data, they go on to report that Black officers make fewer stops and fewer arrests, and use force fewer times than white counterparts, on average. These disparities were not uniform across situations, say the authors, but were driven by a reduced focus on Black civilians by Black officers and a lesser use by Black officers of discretionary stops such as for "vaguely defined 'suspicious behavior.'" Like their Black colleagues, Hispanic officers conducted fewer stops, made fewer arrests, and used force less than white officers, though the gaps were more modest. The findings also show women make fewer arrests, including of Black civilians, and use force less often than men. The authors note limitations of their study, but they say their approach offers a widely applicable template for other scholars to follow when testing whether these findings hold in other places and times. They conclude: "The effects of diversification are likely neither simple nor monolithic. Officers are multidimensional, and crafting effective personnel reforms will likely require thinking beyond the coarse demographic categories typically used in diversity initiatives and consideration of how multiple attributes relate police to the civilians they serve."


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