They performed a test of this during the holidays, by having a uniformed TSA person stand behind the ticket/ID checker. Based on observing the passengers in line, the TSA people pulled over 500 people of interest and asked them questions. They were then either sent on their way, sent to secondary, or sent to secondary and an LEO was called. About 30 out of the 500 were found to be up to "something (mostly drugs, but some people with "too much" money), though none were terrorists.

They're adamant that the program does not use race, and that using race as a factor harms its effectiveness.