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by Peter Moskos

October 14, 2014

Racial disparity in police-involved homicides: 4:1

Trying to set the record straight is a bit like pissing into the wind. The substantively wrong pro-publica story has now been repeated by every news source I can find.

I suspect that over time the idea that from 2010-2012, blacks males 15-19 years-old were 21 times more likely than non-hispanic-whites males to be killed by police will simply become remembered as: police are 21 times more likely to shoot black people. But it's not true! (There I am again, getting spattered by my own pee.)

The real figure they're talking about -- not just the numbers from 2010 to 2012 -- the real figure is not 21 to 1 but 9 to 1. And when one includes hispanics in the count, the black-to-white ratio goes down to 5.5 to 1. If one looks at black and white men of all ages killed by police, the ratio is (just?) 4 to 1. (Ed note: based on later better data, the ratio is actually closer to 3 to 1.)

Now you may wonder why I'm quibbling. What's my point? Well, it's important to base opinions and public policy on fact. And for starters, 4 to 1 versus 21 to 1 is a huge difference.

One could also argue that even a disparity of 4:1 is unacceptable. And it is, on some level. But in the population examined by ProPublica -- the same subset in which blacks are 9 times (not 21 times) as likely as whites to be killed by police -- the black-to-white homicide ratio is 15:1. We know police-involved homicides correlate with homicide and violence in the community they police. So what rate of disparity would one expect in police-involved homicides? Certainly not 1 to 1.

If you're going to honestly talk about racial disparities in police-involved shootings, you need to discuss levels of violence among those with whom police interact. If one thinks police shootings are primarily an issue of racist police -- if one thinks police only shoot black people, if one thinks white people are never stopped by police for minor offenses -- one is not only wrong, but one won't come up with any effective solutions. The vast majority of police-involved shootings are justified. That said, there are bad shootings. But this is more a police problem more than a race problem.

If one wishes -- as one should -- to reduce the racial disparity of police-involved shootings, one needs to focus on racial disparities in crime and violence in general. If one wishes -- as one should -- to reduce the incidences of unjustified police shootings and improper police use-of-force, one needs to improve police training and reduce police militarization.

To replicate the pro-publica study, here are the numbers for the past 15 years (15-19 year-old black and non-hispanic-white men, shot and killed by police and reported to the Uniform Crime Reports). This is the black-to-white ratio for police-involved homicides. All are based on population rates per 100,000 (using constant 2010 census figures, not adjusted for year):

Past 1 year (2012, n = 24): 13 to 1
Past 2 years (2011-2012, n = 45): 16 to 1
Past 3 years (2010-2012, n = 62): 21 to 1
Past 4 years (2009-2012, n = 92): 17 to 1
Past 5 years (2008-2012, n = 110): 17 to 1
Past 6 years (2007-2012, n = 140): 15 to 1
Past 7 years (2006-2012, n = 162): 12 to 1
Past 8 years (2005-2012, n = 183): 10 to 1
Past 9 years (2004-2012, n = 209): 9 to 1
Past 10 years (2003-2012, n = 226): 10 to 1
Past 11 years (2002-2012, n = 249): 9 to 1
Past 12 years (2001-2012, n = 262): 9 to 1
Past 13 years (2000-2012, n = 286): 9 to 1
Past 14 years (1999-2012, n = 312): 9 to 1
Past 15 years (1998-2012, n = 339): 9 to 1

With the above data, you can't say anything conclusive from just the first few years of data. Certainly the group that I would least want to pick and highlight is the three-year (2010-2012) statistical outlier. Cherry-picking the highest number would be dishonest, but even assuming it's just accidental is still shoddy research. One would expect the results to bounce around for the first few years and then settle down. Only then can one find validity -- the idea that the number has any meaning.

Why pick the past three years instead of the past 2, 4, or 15 years? One key to analyzing statistics is skepticism of "amazing" anomalies, especially from a small group. Something can be (in fact, will be 1 in 20 times) statistically significant but substantively irrelevant.

But why is the 3-year cumulative number so high? Because only one non-hispanic white teen got shot and killed by police in 2010. Since the sample is so small, one strange year can screw up the data. But over more years the numbers settle down. Here one needs to go back maybe 8 to 10 years to find any substantive meaning. (And even then all this UCR data on police-involved homicides should be taken with a gigantic grain of salt.)

[Also, there's a bit more rambling detail, in less coherent form, in one and two previous posts. Here's a follow-up post.]


Jay Livingston said...

I haven't looked at the ProPublica statement. But if you use only the number of each race killed, you're going to get a much lower B/W ratio than if you convert that number to a rate per population. There are a lot more White teenagers than there are Black teenagers. If there are five times as many White teens, and if the ratio based on raw numbers is 4:1, then the ratio based on rate per population will be 20:1 -- not that far from the ProPublica ratio.

Of course the real question, if you're interested in the question of police racism, is whether in similar circumstances a Black kid is more likely to be shot than is a White kid. (And I think "shot" is a better variable than "shot dead.")

PCM said...

Jay, all the numbers are already rates per 100,000. I will make that more clear. We're using the same numbers.

The "real question" is that one that can't be answered for sure, of course. But I suspect there is not a significant on the level of individual incident. But the data certainly do not show a higher rate of blacks being killed, if violence is taken into account (Another question is just how much violence should be taken into account. Is it a 1:1 linear relationship? I do not know.)

And yes, shot is better than "shot dead," but we have no good numbers on non-fatal police-involved shootings. And as long as the n is big enough, one can assume some good correlation between fatal and non-fatal, at least within a department. (West coast cops have a higher fatal to non-fatal ration, by the way. Either because they shoot more shots or they use shotguns.)

RobL said...

I just recently came across your posts on the statistics of police shootings and mentioned them on-line. A post by someone else later called into question the basic data being used and cited the following link from FiveThirtyEightPolitics: http://fivethirtyeight.com/features/how-many-americans-the-police-kill-each-year/

The comments relate to the reliabilty of the UCR database against the SHR report.

I would appreciate your comments and clarification.

Peter Moskos said...

This article provides a very good summary of the issue:

But the long and short of it is we don't know how many people police shoot. The number either don't exist or are crap. It's an outrage.

Peter Moskos said...

Also, just to be clear, the SHR is part of the UCR.

But many departments that report data to the UCR don't include the data that is used in the SHR.

jnfphd said...

Nice write up. Can you expand on the 4 to 1 ratio? Seems like the stat is for 15 years comparing black to white "non-Hispanic" men of all ages, but I couldn't be sure.

Peter Moskos said...

The data for hispanic is horrible and I prefer not to use it. The problem is that police, if they record it at all (and many do not) consider hispanic to be a race and the UCR (and census) consider it to be an ethnicity laid over race.
The UCR took hispanic data (when it existed) and coded them all as white.
But yes, what I present above does exclude "hispanics," as coded by the UCR. This is to keep it comparable to the crappy ProPublica data.

Anonymous said...

Please elaborate on the 15:1 black-white homicide ratio you mention. Where does that data come from?

Peter Moskos said...

From the FBI's Uniform Crime Report annual homicide supplement (for the same years and population selection propublica used).

NegroAchievement said...

I wonder what the disparity would be if you used the number from killedbypolice, which tracks all deadly officer involved shootings reported by local media around the country (and it must be only a very small number of such shootings that local news would ever fail to report). The yearly tally is closer to 1000 people killed, you can see the names, age, very often deduce the race, and know the exact circumstances of each shooting to get a clear picture. I spent some time combing through the data but alas it is too time consuming, but very enlightening to go through the cases I reviewed. I strongly suggest the author of this blog use killedbypolice numbers going forward they are the most reliable.

Peter Moskos said...

I recently discovered that data. It is better. But it doesn't change the overall figure much (except in terms of absolute numbers). Please check more recent posts (April 2015).

Start here: http://www.copinthehood.com/2015/04/killed-by-police-1.html

Anonymous said...

According to DOJ data from 1976 black males 13 to 24 were 6 times more likely to kill police. So does this explain why young blacks are killed more? It is certainly something to think about.

Mike Tremoglie