It seems that the '1%' is symbolic, though. Just a round 'very small' number that sounds nice. Probably way less currently, orders of magnitude less.
It seems that the proportion of ground-breaking individuals is less a function of population than of the state of things. Meaning, it doesn't matter how many are trying if there are only ever X slots available for 'greatness' at a given time. E.g. when one Musk or one Gandhi arises, a thousand others might have just missed that spot for this life.
At the very least, there is a relation between the two — pushing population to extreme numbers obviously increases the number of exceptional individuals because there is more need; but I see a rather linear bottleneck here, whereas context dictates a lot of what you can and can't do. In that sense, the greatest are the most adaptive (evolution-style, applied to civilization), they find the 'correct formula' to solve in their own space and time. And execute on it.
I think it's more of a “few thousand people” worldwide at any given time in recorded history, maybe 10x or 100x more today than in Ancient times but... nowhere near the population growth ratio.
Obviously, it's all just my subjective perception. I could be so wrong it's actually not-not funny to think about it... ¯\_(ツ)_/¯