Finding the Right Statistic

Earlier this week, Think Progress reported that at least five black women have died in police custody in the United States since mid-July. The author of that post, Carimah Townes, wrote that those deaths “[shine] an even brighter spotlight on the plight of black women in the criminal justice system and [fuel] the Black Lives Matter movement.” I saw the story on Facebook, where the friend who posted it inferred that “a disproportionate percentage of those who died in jail are from certain ethnic minorities.”

As a citizen, I strongly support efforts to draw attention to implicit and explicit racism in the U.S. criminal justice system, and in the laws that system is supposed to enforce. The inequality of American justice across racial and ethnic groups is a matter of fact, not opinion, and its personal and social costs are steep.

As a social scientist, though, I wondered how much the number in that Think Progress post — five — really tells us. To infer bias, we need to make comparisons to other groups. How many white women died in police custody during that same time? What about black men and white men? And so on for other subsets of interest.

Answering those questions would still get us only partway there, however. To make the comparisons fair, we would also need to know how many people from each of those groups passed through police custody during that time. In epidemiological jargon, what we want are incidence rates for each group: the number of cases from some period divided by the size of the population during that period. Here, cases are deaths, and the population of interest is the number of people from that group who spent time in police custody.

I don’t have those data for the United States for second half of July, and I doubt that they exist in aggregate at this point. What we do have now, however, is a U.S. Department of Justice report from October 2014 on mortality in local jails and state prisons (PDF). This isn’t exactly what we’re after, but it’s close.

So what do those data say? Here’s an excerpt from Table 6, which reports the “mortality rate per 100,000 local jail inmates by selected decedent characteristics, 2000–2012”:

                    2008     2009     2010     2011     2012
By Sex
Male                 123      129      125      123      129
Female               120      120      124      122      123

Race/Hispanic Origin
White                185      202      202      212      220
Black/Afr. Am.       109      100      102       94      109
Hispanic/Latino       70       71       58       67       60
Other                 41       53       36       28       31

Given what we know about the inequality of American justice, these figures surprised me. According to data assembled by the DOJ, the mortality rate of blacks in local jails in those recent years was about half the rate for whites. For Latinos, it was about one-third the rate for whites.

That table got me wondering why those rates were so different from what I’d expected. Table 8 in the same report offers some clues. It provides death rates by cause for each of those same subgroups for the whole 13-year period. According to that table, white inmates committed suicide in local jails at a much higher rate than blacks and Latinos: 80 per 100,000 versus 14 and 25, respectively. Those figures jibe with ones on suicide rates for the general population. White inmates also died from heart disease and drug and alcohol intoxication at a higher rate than their black and Latino counterparts. In short, it looks like whites are more likely than blacks or Latinos to die while in local jails, mostly because they are much more likely to commit suicide there.

These statistics tell us nothing about whether or not racism or malfeasance played a role in the deaths of any of those five black women mentioned in the Think Progress post. They also provide a woefully incomplete picture of the treatment of different racial and ethnic groups by police and the U.S. criminal justice system. For example and as FiveThirtyEight reported just a few days ago, DOJ statistics also show that the rate of arrest-related deaths by homicide is almost twice as high for blacks as whites — 3.4 per 100,000 compared to 1.8. In many parts of the U.S., blacks convicted of murder are more likely than their white counterparts to get the death penalty, even when controlling for similarities in the crimes involved and especially when the victims were white (see here). A 2013 Pew Research Center Study found that, in 2010, black men were six times as likely as white men to be incarcerated in federal, state and local jails.

Bearing all of that in mind, what I hope those figures do is serve as a simple reminder that, when mustering evidence of a pattern, it’s important to consider the right statistic for the question. Raw counts will rarely be that statistic. If we want to make comparisons across groups, we need to think about differences in group size and other factors that might affect group exposure, too.

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2 Comments

  1. The inequality of American justice across racial and ethnic groups is a matter of fact, not opinion, and its personal and social costs are steep.

    -Yeh, those Asians aren’t being arrested or convicted anywhere near enough.🙂 Also, you didn’t mention its personal and social benefits. Or that not all men are created equal.

    Reply
  1. Weekly Links | Political Violence @ a Glance

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