I posted stats (for the BDO program, not for my top secret straw-into-gold process) from 2009. The stats about which you said "I dont believe those were ever published." They aren't pretty: 99.21% of people stopped by BDOs for further investigation were found to be blameless.

If more recent statistics show an improvement, why isn't TSA pulling them out to refute the DHS IG?

Even Paul Ekman, who as GUWonder pointed out, has a vested financial interest in having the gov't use his work, said that the system "needs more study", yet TSA, in the 7 years that they've been playing SPOT, have just assumed that it works.