0.01%
Just a guess. You could probably put a few more zeros after the decimal point, if you only include plans filed prior to flight.
You can use an AFPEx account to file plans for free, provided the account generates fewer than 20 messages a day. Ours certainly does fewer than that. You can file via Sky Demon, but that costs, if you take into account the
cost of the Sky Demon package. There are other 'GA' packages available, but as far as I know in the UK, AFPEx is the only one that is free to the user.
Some people fail to realise that requesting to cross controlled airspace once airborne, a common enough practice for Class 'D' constitutes filing a flight plan, so maybe you could move a couple of zeros back again.
TOO