Maybe measure anyone who gets to Biggin/Cranwell, and look at the percentage of those reaching a squadron. If you got that far and washed out before CR, I reckon you earned the right to say, "Iwas a fast jet pilot/(insert the branch of interest). I was NCA (airman aircrew in imperial units!), so'd like to see those numbers.
It would be a better yardstick than that old chestnut, 'you're in the top x% of the population': most of the population couldn't give a fig!
CG