When I did it, on my courses 43% of EFT went, 52% of BFT, 43% of AFT, 14% of TWU and 11% of the OCU. The overall attrition rate was 37%.
Then when I was Operational, I knew well 10 guys killed before they reached their 30th Birthday in peacetime accidents, I had dinner with 3 of them in the week before they died and watched one walk out of the office at 0730 never to return.
Maybe that is why the chop rate is so high!