Circles in the map below are scaled according to the number of sworn officers in each police department. As shown in the blue legend at bottom, the shade of each circle indicates the size of the race gap between the police force (sworn officers) and the population; the darker the circle, the larger the gap. General population demographics are sourced from the 2010 U.S. Census Bureau; police force demographics are based on the Bureau of Justice Statistics' police force questionnaire from 2007 (see below the map for additional notes and methodology).
Darren Wilson, the police officer who shot and killed Michael Brown last August, was one of 50 white officers on Ferguson's 53-member police force. That's in a city with a two-thirds black population.
The wide race gap between Ferguson's police force and its community is not unusual. A recent New York Times analysis of 2007 government survey data on local police demographics found that hundreds of police forces across the country are more than 30 percentage points more white than the communities they serve.
This is no exception in many Bay Area cities. In our own analysis of data collected from the federal Bureau of Justice Statistics' police force questionnaire from 2007 -- the most recent comprehensive data available -- at least 10 cities in the region have police forces that are more than 30 percentage points more white than the general population of the communities they serve.
While it's unclear to what degree police demographics affect community relations in specific cities -- as opposed to factors such as residency -- many law enforcement experts agree that more diverse police forces often gain greater credibility in the communities they serve.
"Police departments have struggled to achieve diversity for several decades now," says Justin McCrary, a professor of law at UC Berkeley who studies police demographics and is director of the D-Lab.
"One of the major problems departments confront is hiring qualified applicants. Most are averse to putting any restrictions on their pool of applicants."
He argues, though, that if more people in the community had a better awareness of the decent pay and excellent benefits that come with most law enforcement positions, the diversity and size of the hiring pool would likely increase.
"Enlisting the support of community leaders really helps police departments bridge that gap, particularly when a department is struggling with community relations.”
-- Data for each police department, except Hayward, was derived from the 2007 Bureau of Justice Statistics (BJS) survey, the most recent comprehensive data available (although some police force ranks have likely changed since then). Only cities that participated in the survey are included. View the data set here.
-- Individuals enumerated in the BJS survey as American Indian or Alaskan, Native Hawaiian or Pacific Islander, two or more races, and "Other" are combined here as "Other."
-- In five of the 28 police departments, the race or ethnicity of some officers was unknown. For each of the five departments, this group comprised less than 5% of the total police force. These officers are included here as "Other."
-- Racial demographic data on the Hayward Police Department was not provided in the BJS survey. It is, instead, sourced here from the City of Hayward's 2013 Commission on Accreditation for Law Enforcement Agencies, Inc. Assessment Report. The report includes only White, Black, Hispanic, or Other.
-- From the BJS questionnaire:
"The BJS collects data from over 3,000 state and local law enforcement agencies, including all those that employ 100 or more sworn officers and a nationally representative sample of smaller agencies. Data are obtained on the organization and administration of police and sheriffs' departments, including agency responsibilities, operating expenditures, job functions of sworn and civilian employees, officer salaries and special pay, demographic characteristics of officers, weapons and armor policies, education and training requirements, computers and information systems, vehicles, special units, and community policing activities."
Ryan Mah, Andrew Cohn and Lisa Pickoff-White contributed to this project