I'd like a statistician to look at those numbers and tell me if an 8% differential is really a huge gap.
It seems to me that the real difference is the ability for Nadal to dominate on one surface, and Federer to dominate on two. Also another variable is the number of years each has been playing. I know you think the percentages account for that, but I think it doesn't completely.
Also, do you make a distinction between indoor surfaces?
I think it would be quite interesting to take the percentages from this 12 months past and see where those percentages are, and then keep track of it each year.
p.s. Thanks for compiling those numbers!
It was interesting to look at.