Originally Posted by
gingersnaps
Most Fake Bombs Missed by Screeners 2007
"Tests earlier in 2002 showed screeners missing 60% of fake bombs. In the late 1990s, tests showed that screeners missed about 40% of fake bombs, according to a separate report by the Government Accountability Office, the investigative arm of Congress."
What is interesting is that as of 2015, according to DHS Inspector General John Roth private screeners fair no better than TSA, yet the above 2007 article suggested they did. According to the article and a CNN article covering the same topic, private screeners were constantly tested. Today though neither group is better than the other.
As much as I dislike TSA, there is a genuinely difficult aspect to every screener's job, which is that the vast, vast, vast majority of the baggage and passengers they screen don't present a threat. In that sort of environment, it's really hard not to glaze over.
If memory serves, one of the aircraft engine manufacturers had a similar problem with people inspecting jet engine turbine blades. Defects were so rare that, one the very rare case somebody did come across one, they were likely to miss it, since they might go through thousands of blades before finding a defect. So, they started intentionally introducing a very small number of defects before the blades were inspected, to keep the inspectors mentally engaged. These weren't lazy or incompetent people - they were just human.