A major problem inherent in dealing with security against terrorism via political means is the tendency to focus what are always scarce resources on highly visible efforts—what some have termed “security theater.” The alternative is to base security policy on serious risk analysis, putting resources where they achieve the greatest bang for the buck. That kind of analysis in aviation security suggests that spending $4 billion per year on screening every passenger and bag (rather than focusing resources more on higher-risk passengers) and stationing air marshals on airliners are not cost-effective uses of security dollars. If we spent less of these resources on security theater and more on preventing airfield perimeters from being breached and lobbies from being targeted by suicide bombers, we’d likely be better off. And by the same token, serious risk analysis might suggest spending relatively less on aviation security and relatively more on rail and cargo security.

Focus on detecting means, and motive becomes irrelevant ...