It's low enough to be statistically insignificant.  I saw 4 characters in 1e who had rolled psionics (2 at the same table, oddly enough), maybe 2 that I recall in 2e.  3.x I saw two.  I never saw any in 4e but I didn't play that edition much.
That's outside of campaign settings where psionics are a prominent feature. In a typical campaign it was almost non-existent.
				
			That's outside of campaign settings where psionics are a prominent feature. In a typical campaign it was almost non-existent.