Risk Factors in Police Brutality

UPDATE: Updated information about African American population in the south (because it’s higher than the rest of the country, 20% vs 12%)

On Tuesday night there was another civilian killed by police during an arrest, this time in my hometown of Baton Rouge. Alton Sterling was shot 6 times last night, making the national news in the most recent act of police brutality. Let’s sift through the data to see if we can find any trends.

DISCLAIMER: I am not making ANY stance on the issue here, I’m just looking through the data we have a little better than the guys at 538 did…

The Data

The data can be found here and contains incidents of police killing civilians from 2013-December 31 2015. They do a pretty comprehensive analysis on the bare numbers, noting that in 2015 5 times more unarmed African Americans were killed than unarmed White and Hispanic people. They do a summary of data in 2015 here. This data consists of the 3845 cases of police brutality since 2013. Also shockingly, between 2013-2016, there have been only 77 days where there was not a civilian killed by police!

Covariates considered

The data consists of many variables but in particular I will focus on the following ones:

Race: The breakdown of the data by race is shown below:

So as we can see the three biggest categories of civilians killed by police are Caucasians followed by African Americans, and Hispanic people. The rest I will group together as “other”

Gender: The breakdown of data by gender is shown below:

Clearly we have some mislabeling in the data here, as there’s not a White Gender and there is also some missing information. I’m only going to consider cases where the victim’s gender was male or female and will throw the rest out.

Did the Victim have a weapon: 

I’m not going to look at the Unclear cases here, just weather or not the victim was armed or unarmed. I’m also not going to look at the cases involving a vehicle. The “unarmed” status here indicates whether they were visibly unarmed (including toy guns) at the time of being killed. This also includes cases where police said they we’re armed but other first hand witnesses disproved this assertion.

Region of U.S.: Take a look at the breakdown of the data by state

The states with the most police violence are California, Texas and Florida. There were also many incidences in Arizona, Georgia, North Carolina, New York, Ohio and Washington. So let’s break it down by region into Northeast, Southeast, West and Midwest.

So it looks like the South and West are the biggest culprits, with the Northeast having the lowest incidences of police brutality.

Age: Take a look at the histogram below of all available ages

As you can see most victims were between 20-60 years old, with a maximum age of 107 (which is pretty awful). It looks like it has a quadratic form as well.

After throwing out the cases I mentioned above, we are left with 3163 incidences of police brutality and a quick summary of the above covariates for this reduced set is shown below.

So we see that there’s not a big difference in the proportions of victims who were armed within each racial group. However, we should note that 37% of the unarmed people killed by police are African-Americans, while they only make up 12% of the population. This is very disproportionate and points to what the recent protests are about. It’s always a tragedy when unarmed people are killed by police, even if they actually are committing a crime, and this tragedy happens disproportionately to African-Americans.

Now let’s look at the breakdown of incidences by region and by Race:

There were way more African Americans and Caucasians Killed in the South than in other regions and there were drastically more Hispanic people killed in the West than the rest of the country. But the biggest thing I found through sifting through this data shows up when we break down the police brutality by region, race and Armed status.

Southern Police kill unarmed African Americans more than any other race, encompassing about 48.6% of unarmed southern shootings. Since African Americans (table 5) make up about 20.11% of the southern population (from the 2010 census), this should be alarming.

But this is just data, you draw your own conclusions. There is definitely an issue here with police brutality and it has not gotten any better over time.

If you enjoyed this post, take a look at some of my other Adventures in Statistics.

-Andrew G. Chapple