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.]