The strategic nuclear people claim that Deterrence Worked. In this arena, some believed that perception was more important than reality.
The GAO recently gave TSA a failing grade on security at airports.
The last thing we need is a scientific study to determine the probability of finding (or missing) items in our airport scans.
A new device might find something new.
When I was doing my thesis research at Argonne National Laboratory, the word going around the team was there was a mathematics professor at the University of Illinois, who after learning that the probability of a bomb being in someone's luggage was 1 in a million always put a bomb in his luggage so that the probability that there would be another bomb on his plane would be 1 in 10**12.
People have very strange beliefs about probability.
All you people who never plan to fly, talk up how porous our security system is.