Re: Logic and Racial Disparities

I greatly appreciate that John K. Roman and Shebani Rao took the time to respond to the post I wrote earlier this week. As a journalism-school graduate, I certainly have no right to be taken seriously by such high-caliber analysts.

To summarize briefly: The data indicate that white-on-black homicides are much more likely than black-on-white homicides to be ruled justifiable. I argued that this can be explained by racial differences in offending: Because interracial violent crimes are more likely to involve black offenders and white victims, whites have more opportunities to commit justifiable homicide. In addition, whites are far more likely to own guns, so, when faced with an opportunity to commit justifiable homicide, they are more likely to have the means to do so.

This is the crux of their response:

Suppose we assume that a racially unbiased system would have the same rates of justifiable rulings regardless of race. To see what that would look like, we use the average rate homicides are ruled justifiable from the FBI data -- 2 percent. At the 2 percent FBI rate, we would expect to find that out of 128,000 white-on-black victimizations reported in the National Crime Victimization Survey (NCVS) data, about 2,500 would be ruled justifiable. And, out of the 767,000 black-on-white victimizations almost 15,000 would be ruled justified. However, if instead we use the actual rates from the FBI data at which white-on-black homicides are ruled to justified (11.41 percent) and black-on-white homicides are adjudicated justfied (1.2 percent), it paints a very different picture: Using these numbers, 14,600 white-on-black victimizations would be ruled justified, compared to only 8,800 black-on-white victimizations. Thus, it is clear that racial disparities in homicide rulings remain.

The first sentence is where I see the flaw to be. Roman and Rao simply assume that violent offending and justifiable uses of violence go hand-in-hand; if one group is more likely than another to offend, that group must also be more likely to engage in justifiable violence. But this begs the question: What we are debating, after all, is whether different groups might have different ratios of justifiable to unjustifiable violence -- that's the trend in the FBI data that everyone found so striking, and that I was trying to explain by something other than racism on the part of decisionmakers in the criminal-justice system. The authors haven't shown my argument to be wrong; they've just assumed it's wrong.

Further, I believe this assumption does not hold up to scrutiny. Justifiable violence is something one does only when provoked by unjustifiable violence, and thus a group's rate of justifiable violence must vary, at least in part, according to the rate at which its members are victimized. I'd like to illustrate this with both a thought experiment and a more concrete analysis.

Imagine a society with two social groups, Group A and Group B. Each group commits 100 violent offenses against the other, and of those offenses, 10 lead to justifiable homicide by the victim, for a ten-to-one ratio. But for whatever reason, over time, Group A begins to offend at twice the rate, committing 200 violent offenses against Group B.

If we assume that each group's proportion of justifiable to unjustifiable interracial violence remains constant, here's what happens. Group A now commits justifiable homicide in 20 of the 100 offenses committed against it -- which isn't crazy; maybe the same factors that increased the group's offending rate also increased its members' willingness or ability to use lethal force in self-defense. But Group B still commits just 10 justifiable homicides, despite having twice as many opportunities -- i.e., a randomly selected person from Group B will have a 5 percent chance of defending himself when attacked instead of a 10 percent chance, even though his odds of being victimized in the first place have doubled.

This strikes me as highly implausible -- and what's more, in extreme enough situations it's mathematically impossible for the authors' assumption to hold up in this hypothetical world. If Group A commits 1,500 violent offenses, it would have to commit 150 acts of justifiable violence to keep the ratio at ten-to-one, even though Group B gives it only 100 opportunities.

So, it doesn't surprise me that calculations done under this assumption don't explain the FBI's data on justifiable homicides. Further calculations reveal some rather questionable results. According to the authors' numbers, based on the NCVS data, we would expect there to be 2,500 justifiable and 125,500 unjustifiable acts of violence by whites against blacks, and 15,000 justifiable and 752,000 unjustifiable acts of violence by blacks against whites. This means that blacks defend themselves against whites roughly 12 percent of the time, while whites defend themselves against blacks 0.3 percent of the time.

I won't profess to know the best way to model the interaction between groups' offending rates, their victimization rates, and their justifiable-violence rates. But it's at least worth redoing the authors' calculations under the opposite assumption. Let's say that 2 percent of all offenses inspire justified violence by the victim* rather than that they are themselves justified.

So, 128,000 acts of white-on-black violence inspire 2,500 acts of justified violence by blacks. And 767,000 acts of black-on-white violence inspire 15,000 acts of justifiable violence by whites. This shifts the numbers around: Both whites and blacks defend themselves when attacked 2 percent of the time, as per our assumption -- but as a result, 10 percent of white-on-black violence is justified, and only 0.3 percent of black-on-white violence is. This corresponds closely to the actual disparity from the FBI figures: 11.41 percent to 1.2 percent. And we haven't even gotten to my other argument, that whites are more likely to own guns and thus are more able to commit justifiable homicide when the situation calls for it.

Again, this is a rough exercise. I wouldn't dream of claiming I've proven that there's no racism in play here. But it still seems that these results can be explained by other factors.

Robert VerBruggen is editor of RealClearPolicy. Twitter: @RAVerBruggen


*Technically, it would be 2.04 percent in order for the inspired actions to constitute 2 percent of the inclusive total, but 2 percent will do for a ballpark estimate.

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