Explaining the Grand Rapids Police Traffic Stop Study

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Results presented to the City by Lamberth Consulting. Photo source

A few weeks ago, Grand Rapids released their study on racial bias in the Police Department. It was found that on average, Black motorists were 2X more likely to be stopped than expected in 2015. This has increased from 1.85X in 2013 and 2014 and 1.4X in 2004. As one of the data collection leaders on the study, as well as having experience in social research, I have decided to address some of the outrage that select members of law enforcement expressed when I posted the findings last month on my LinkedIn page.

First, I would like to address those who attacked the credibility of the study by calling myself and other surveyors “college kids,” who were “not encouraged to find the true results.” This study was conducted by Lamberth Consulting, a company that has conducted this same study in more than 25 cities across the country. In 2005, Dr. Lamberth also addressed the UN Minority Forum. Do not think that this study was done by amateurs.

As previously stated, I was one of the people collecting data at intersections. The reason we collected data at intersections was because we wanted to see who was driving in certain areas of town and compare that to who was getting stopped. This is the beauty of the methodology.  Instead of only examining the racial makeup of people who reside in a neighbourhood and comparing it to who is stopped, the study wants to know the makeup of the people simply driving through a neighbourhood. This is important because we don’t only get pulled over where we live, and the demographics of who is driving in certain neighbourhoods changes based on the day of the week or the time of day. For example, on a Saturday night you will get different people heading into the city than you would during rush hour traffic, and we wanted to account for those changes. The data on who was driving through the intersections was then compared with who was ticketed near those intersections.

What I want to stress when talking about the findings is this: the study does not say that more black motorists are being stopped. It is saying that Black motorists are 2X as likely to be stopped than non-Black motorists. This was one of the major misunderstandings by those who criticised the study.

Say for example that 100 people pass a police officer, 50 Black and 50 White. If the cop pulled over 10 people at random you would expect 5 to be Black and 5 to be White. Instead, what was actually observed is something closer to 7 Black people being pulled over and 3 White. Now it may be by chance that 7/10 people pulled over are Black on a single day, but if that were the case spanning an entire year, there is something deeper going on, and that ratio becomes more significant.

But Grand Rapids is not 50% Black and 50% White so let’s look a little more in depth.

Let us say now 100 people drive by the police officer and 20 are Black and 80 are White. We would expect 2/10 people pulled over to be Black and 8/10 to be White. Instead, what this study told us that it would be more like 4 people are Black and 6 are white. While overall more white people are being pulled over, only 6/80 White people driving by are stopped as opposed to 4/20 who are Black. The ratio is what is important, not the hard data.

While the study was more in depth, and has more variables, this should be able to help you understand that while more White motorists are pulled over in the city by sheer number, Black motorists are pulled over disproportionately.

Now some of you may think that those Black motorists had a reason for being pulled over at a higher rate. Well, there was a second part of the study that looked at searches. It found that when there is probable cause, Black motorists are statistically less likely to be carrying contraband, and when there is a consent search there is no difference between the groups. This finding directly conflicts with the argument that Black motorists are pulled over more often because they are more likely to be carrying contraband. Despite these findings, Black motorists were 3.97X more likely to be searched in 2013, 3.07X in 2014, and 2.54X in 2015. This decreasing trend shows promise, but overall the study showed startling data to the racial bias that exists in the city of Grand Rapids.

This is an important issue facing not only the United States, but the entire world. Civil servants need to know that we support their attempts to reform law enforcement. Despite the backlash, the mayor and city planner of Grand Rapids intend to use this data. There has been a minority voice that supports them in their decision, including my own voice. I called the mayor to let them know that I support their initiative to reform law enforcement in the city, and also to ensure that this study does not get forgotten.

Further Resources

Implicit Bias Test: Take this as a self assessment. Don’t be discouraged. I would argue we all have some sort of implicit bias. Learn from it and make active changes in your daily life to address your bias.

Calvin Chimes Article

MLive article


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