Despite finding no evidence of significant statewide bias, Washington State Patrol officers disproportionately pull over Black drivers in King and Pierce counties, according to a study by Washington State University researchers.
The study, which examined 3.4 million traffic stops between Jan. 1, 2015, to Dec. 31, 2019, found that no groups were “significantly” over-represented in officer contacts or calls for service, according to the study.
The study compared the officer contact data with census data. A demographic is over-represented if they are stopped at a rate higher than their proportion of the statewide population. The study defines “significant over-representation” as a difference of 5 percent or more.
However, there were still disparities in officer-initiated contacts, according to the study. Black drivers made up 5.7% of officer-initiated traffic stops during the four years examined despite only making up 4.3% of the total population in Washington, according to the Office of Financial Management.
In 2019, that disparity was even larger and Black drivers accounted for 6.2% of all stops initiated by state patrol officers, according to the study.
White people made up 74.4% of officer-initiated traffic stops despite making up 78.2% of the total state population, according to OFM.
The disparities between Black and white drivers was even higher in King and Pierce counties, according to the study. In King County, 11.5% of officer-initiated stops were of Black drivers, who make up 7% of the county’s population. White drivers made up 62.3% of stops, but 66.2% of the county’s population.
In Pierce County, Black drivers are significantly over-represented in officer-initiated stops as they made up 12.7% of stops, but 7.7% of the total county population. Conversely, white drivers are underrepresented, making up 68.8% of stops and 74.3% of the county’s population.
The researchers at WSU created a disparity index to determine if disproportionalities exist for ethnic or racial groups on a statewide level. The index shows that white people are stopped at a rate that would be expected considering their proportion of the population.
Black drivers are over-represented when compared to their proportion of the population and all other races are underrepresented, according to the study.
In addition to this, the study found that Black, Hispanic and Native American drivers were more likely to be searched by WSP officers than white drivers, according to the study.
Despite being less likely to be searched, white people were more likely to actually have contraband compared to Black and Hispanic people between 2015 and 2019, according to the study. Native American people were less likely to actually have contraband compared to white people in 2018 and 2019, despite being searched more often, according to the study.
The study concluded that this could indicate WSP officers have lower probable cause standards for Black, Hispanic and Native American drivers compared to their white counterparts, according to the study.
WSU researchers plan to continue working with the WSP to address the disparities for Black and Hispanic drivers, according to the study.