Grim-faced border guards and tough security measures at international airports provide powerful reassurance that the developed world is spending hundreds of billions of dollars to protect against terrorism. But is it worth it?

Although citizens of rich countries regard terrorism as one of the world's greatest threats, trans-national terrorists take, on an average, just 420 lives each year. So, have the terrorists succeeded in getting the developed world to invest poorly in counterterrorism, while ignoring more pressing problems involving health, the environment, conflict, and governance?

Recently, the Copenhagen Consensus, whose purpose is to weigh the costs and benefits of different solutions to the world's biggest problems, commissioned new research into the merits of different methods of combating terrorism. The results are surprising and troubling.