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Political Diversity in U.S. Police Agencies

Jonathan Mummolo, Associate Professor of Politics and Public Affairs, Princeton University
Encina Hall West, Room 400

Partisans are increasingly divided on policing policy, which may affect officer behavior. We merge rosters from 99 of the 100 largest local U.S. agencies—over one third of local law enforcement nationwide—with voter files to study police partisanship. Police skew more Republican than their jurisdictions, with notable exceptions. Using fine-grained data in Chicago and Houston, we compare behavior by Democratic and Republican officers facing common circumstances. Overall, we find few partisan differences after correcting for multiple comparisons. But consistent with prior work, we find Black officers make fewer stops and arrests in Chicago, and they use force less in both cities. Comparing same-race Democratic and Republican officers, we find only that White Democrats make more violent-crime arrests than White Republicans in Chicago. Our results suggest that despite Republicans’ preference for more punitive law enforcement policy and their overrepresentation in policing, partisan divisions do not translate into detectable differences in on-the-ground enforcement.


I am an Associate Professor of Politics and Public Affairs at Princeton University. I study bureaucratic politics and political behavior, and devote particular focus to law enforcement agencies and police-civilian interactions. My work explores several facets of policing, including how controversial tactics are deployed in time and space, how rules and procedures affect the nature and volume of police-civilian interactions, the role of race in police behavior, and how police tactics affect perceptions of law enforcement and crime. 

I also conduct methodological research on issues relevant to my substantive work, including causal inference, statistical modeling and experimental design. My work exploits a range of research designs and data sources including field, natural, and survey experiments, qualitative interviews and administrative records obtained through public information requests to government agencies.

My research has appeared in American Political Science ReviewThe Journal of PoliticsProceedings of the National Academy of SciencesJournal of the American Statistical Association, and Science, among other peer-reviewed journals. I received a B.A. from New York University and a Ph.D. from Stanford University. Before beginning my doctoral studies I was a staff writer at The Washington Post where I covered crime and politics in the Washington, D.C. region.