The drop rate post PPL is huge, but I don't think it's as high as 90% after the first year. If I remember correctly, it's around 75% after a couple of years. To be honest though, the exact figure is irrelevant, it's ridiculously high.
It really is a travesty that the flight training industry is just that, only seemingly interested in training for initial licence issue, but some of the blame must go onto the govt. as well. With Fuel being so crazily expensive due to tax, the cost of a/c hire is still prohibitively high, most people seem to be able to justify the cost when they have a goal (licence issue) but as soon as they are flying only for pleasure, then other factors come into play (the home front if you like).
The club I help to look after was set up specifically to try and reverse this trend, by offering something for the PPL holder. Firstly we have good a/c availability and a wide range of more touring based machines as well as the more usual training orientated a/c. This allows members to have good availability as they aren't competing with the training side in any way. In fact we have more PPL members than we do students. Couple this to actively getting people to meet up and share flying, experiences etc. It gives a good base for people to try out new things and get their confidence up whilst sharing the cost and getting a good social element built in.
So far it seems to be working well and none of it is rocket science (can't be if I have anything to do with it!) if we can help even a small bit to try and reverse this crazy trend of dropping out after just a few flights post licence, then I'll feel happy.
Good well, equipped a/c help alot as well!