Less than 1% - it's less than 0.03%.
Depending of the source of the survey and the purpose avg varies.
A study of the urology dept at the university in Leuven; sponsored by Durex; found what we allready knew.
A penis is between 84mm (3.3") and 198mm (7.8") 99.8% ( sigma 3 ) erect non bone pressed.
That means that only 0.2% is out of these limits.
So we can conclude that 8" exist; 9",10" very rare and above 10" honestly it will exists like 6 fingers on a hand.
Look at porn - you see seldom a penis over 9".
