Looking at the gliding National Ladder for 2010
there are 4698 flights logged
Well, that's not really a random sample, is it? I mean, if you go through the trouble of signing up with the ladder, buying the logger devices and so on, you're already in the moderate-to-high endurance bracket, I'd say. Or are you really saying that the whole glider community in the UK only managed 4698 flights, altogether, over the whole of 2010?