One of my liberal de Blasio-loving not-so-fond-of-cops friend send me an email with the subject "you gotta check yo facts" and a link to ProPublica: "Young black males in recent years were at a far greater risk of being shot dead by police than their white counterparts – 21 times greater."
"Well, that's interesting," I thought, "It also can't be true." Since I kind of know these numbers (and had discussed them with my friend). So I guess I do have to check my facts. I then wasted a half day running the numbers myself (when I could have been giving my undivided attention to the Orioles' loss).
Now it's always dangerous to say my numbers are right and theirs are wrong. But I trust my numbers, because I just ran them. And I'm good at this. And then I ran them again. I'd like to see their numbers because, well, I think they're wrong. But clearly one of us is wrong. I hope it's not me.
In the past three years (2010-2012) among those 15-19 year old, 54 blacks and 36 have been shot and killed by police. This is according to the UCR stats that are not perfect. But while the data here are not complete, they're OK in many ways. And the black-white ratio should hold-up just fine.
If my data are wrong, please do correct me.
In the 15-19 population population, there are 8,728,271 white males. (Click through to: "Annual Estimates ... by Sex, Age, Race, and Hispanic Origin") There are 1,978,081 black males, 15-19 years-old (2010 census).
Per year, for the past 3 years, this is a police-involved homicide rate of 0.14 per 100,000 for whites and 0.99 for blacks. 0.91 divided by 0.14 is 6.5, not 21. For the past three years black males 15-19 are 6 or 7 times more likely than white males to be shot and killed by police, not 21 times.
The 1,217 deadly police shootings from 2010 to 2012 captured in the federal data show that blacks, age 15 to 19, were killed at a rate of 31.17 per million, while just 1.47 per million white males in that age range died at the hands of police.Now even if one takes a 3-year rate per million (which is statistically odd for two italicized reasons), the rate for blacks is 30 (close to 31 but not replicated). Where I think the error lies is that the rate for whites is not 1.47 but rather 4.3. That's a big difference.
My numbers are based on the years 2010-2012: 36 whites shot and killed. 8.7 million white males 15-19.
[Their 95% confidence interval is vast: "between 10 and 40 times greater risk." This, leaving aside the wrong number, seems to me to be a gross misuderstanding of confidence interval. The overall number (the "n," in stat terminology) of young people killed by police over the past three years is not large. But there's a difference between a small "population" and a small "sample" size.Well conveniently you can just add more years to get a larger population. I don't know why they didn't. (Well, I suspect because it's work. It's a bit of a pain to download and select from each year's UCR sample. But that is what researchers do. I mean, I just happen to have the last 15 years compiled and ready to use because, well, that's what researchers do. On a Saturday night. While watching baseball.)
A confidence interval tells you the odds your sample reflects the total population. Say you ask 100 potential voters if they would vote for Obama. Four or 40% say yes. So what are the odds that Obama would win 40% of the vote? Well you don't know for sure because you didn't ask everybody. But based on those 100 you did ask, you can come up with a range, say 35-45 percent, at which you can say there is 19 in 20 chance that if we did ask everybody, it would be in this range. That's a confidence interval.
Again, if I'm wrong here, correct me! It's been 18 years since I took a statistics class in graduate school. And I wasn't even good at it.
If you poll everybody -- if you have an election -- you don't have a confidence interval. You have a result! Even with its flaws, the UCR is pretty complete. If blacks are X-times more likely to be killed, that's that! There is not a sample but a population. You don't have a confidence interval if you sample everybody in a population. You have a number. But it is a small population.
I also wonder why they only picked people shot and killed, rather than all persons killed. It's a minor difference, but why make more work when you don't have to? 99.2 percent of people killed by cops are killed with a gun.)]
So instead of looking at the past three years, let's increase the population by looking at the past 15 years. From 1998-2012, 210 white and 242 black male 15-19 year-olds have been shot and killed by police. This comes out to an annual rate of 0.16 (per 100,000) for white males and 0.82 for black males.
So over the past 15 years black male teens are 5.1 times more likely -- five times more likely -- than whites to be shot and killed by police. Five times; not 21.
Now maybe 21 and 7 and 5 are close enough for you. Or maybe you think 5 times more is 5 times too many. But what number would be OK? Given ration disparities in violent crime, one shouldn't expect 1:1. One might expect police to be more likely to shoot and kill people who shoot and kill other people. (Remember that we're using rates here, which take into account the population difference, that there are 7 whites for every black in America.)
The homicide rate for black men 15-19 is 9 times the rate for white men. (From 2010 to 2012, looking at men 15-19, 2,382 blacks and 1,209 whites have been murdered by criminals. The homicide rate for these young white men is 4.6 per 100,000. For these young black men, the homicide rate is 40.7.)
So given the 9:1 racial disparity in the homicide rate among young men, what racial disparity would one expect in police-involved shootings? There's no right answer to this question. But I don't think it's unreasonable for the racial disparity of those young men shot and killed by police to be reflective of the racial disparity in violence and homicides among young men. And in fact, the police-involved ratio, at 5:1 (not 21:1 or even 9:1), is much less.
[Updated to reflect population data from 2010 census rather than ACS estimate. It doesn't change much. Also, see next post and my summary.]