Daniel Benjamin has an excellent piece in Slate on the difficulty of measuring terrorist threats. The common way to measure it is body count: if the number of people killed annually by a terrorist group goes down, then the threat from that group is reduced. This measurement also allows people to say things like, “Only 100 people died in the United States this year from terrorism, whereas 3,000 died from gang-related deaths. So gang-related deaths are more of a problem and we should shift resources accordingly.”
As Benjamin points out, the problem with the body count metric is that it does not capture the real danger of terrorism: severe economic dislocation and government overreaction. Of course, both are predicated on people and officials reacting in ways that are way out of proportion to the actual physical threat, but that is precisely the response that terrorism is designed to provoke. Books, like the useful Infernal Machine, document these overreactions and lament that people don’t respond more sanely. But this lament betrays a reliance on the body count metric, which is misleading.