America's Flimsy Fortress

Terrorist attacks are very rare. So rare, in fact, that the odds of being the victim of one in an industrialized country are almost nonexistent. And most attacks affect only a few people. The events of September 11 were a statistical anomaly. Even counting the toll they took, 2,978 people in the US died from terrorism in 2001. That same year, 157,400 Americans died of lung cancer, 42,116 in road accidents, and 3,454 from malnutrition.

Even defending against a specific threat is very difficult. Security is only as strong as its weakest link; three locks on the front door do little good if the back door is open. Likewise, the air transportation system is only as secure as the country's most insecure airport, because once someone passes through security at one location, they don't have to do so at another.

Many of the security measures we encounter on a daily basis aim pinpoint the bad guys by treating everyone as a suspect. The Department of Homeland Security counts on technology to come to our rescue: databases to track suspected terrorists, facial recognition to spot them in airports, artificial intelligence to anticipate plots before they unfold. But that creates a problem similar to the one you see when airport security screeners waste their time frisking false alarms. Terrorists are so rare that any individual lead is almost certainly a false one. So billions of dollars are wasted with no assurance that any terrorist will be caught. When an airport screener confiscates a pocketknife from an innocent person, security has failed.