The Three-Way Terrorism Trade-Off

This pre-9/11 article from the Journal of Law & Economics has disturbing implications for the fight against terrorism. The article demonstrates an unavoidable trade-off among three different goals of the justice system: lowering the crime rate, minimizing the number of innocents convicted, and treating individuals equally before the law (e.g., using the same rules of evidence for all people). The trade-off between the first two goals is probably obvious. But this article takes the argument a step further, by pointing out that our attachment to procedural equality could entail punishing more innocent people.

To put it another way, suppose we hold the crime rate constant. Then applying the same procedural rules to all groups implies jailing more innocent people than if we treated groups differently. The only way to avoid that trade-off is to accept an increase in the crime rate. Here’s how the abstract puts it: “Specifically, we estimate that innocent black Americans would be roughly eight times more likely to be wrongly convicted of murder than innocent white Americans if society placed no value on equality when it comes to convictions. However, we estimate that eliminating inequality entirely could cost up to 1,900 lives annually because of a rise in the murder rate.” (Note that the form of equality referred to here is procedural equality, not equality of conviction rates across groups.)

What’s the logic? Say you’re playing blackjack, and you’re a good card counter. You’re halfway through the shoe, and you know that a disproportionate number of 10-valued cards remain to be dealt. Then it makes sense for you to increase your bet. You would be foolish to make the same bet on every hand, ignoring the information garnered by card-counting (unless, of course, you’re worried about getting kicked out of the casino). Changing your bet based on the count won’t guarantee you better results on every shoe, but you will do better in expected value and over the long haul.

The article’s argument, in a nutshell, relies on the same point. If you know that members of different groups have different probabilities of having committed the crimes they’re accused of, then insisting on the same standards of evidence or burden of proof across groups is equivalent to betting the same amount on every hand, regardless of the card count. You’re throwing away valuable information. Now, there might be very good reasons for doing so – equality before the law is nothing to sneeze at – but there’s no avoiding the trade-off. Ignoring that information means either (a) accepting a higher crime rate (which means innocents getting hurt), (b) punishing more innocent people (again, innocents getting hurt), or (c) both.

Now apply this lesson to the war on terror. Instead of talking about conviction of crimes, we can talk about apprehension of potential terrorists by means of airport searches, detainment, and so on. If we insist on treating everyone equally regardless of ethnic background (i.e., no ethnic profiling), we either (a) accept a greater likelihood of successful terrorist acts, or (b) harass a larger number of people, or (c) both. If it’s indeed the case that Arabs are more likely than non-Arabs to be terrorists (as a proportion of their group’s population, not as a fraction of all terrorists), then the trade-off here is quite real. I’m not actually advocating that we abandon procedural equality and embrace ethnic profiling, but I think we should at least recognize the sacrifice.