The stats are not hard to look up, but they do seem somewhat hard to gather. The site you linked doesn't reference a study, but I imagine that asking a bunch of people if they pulled out "perfectly", even for quite stringent definitions of "perfectly" will result in quite a lot of variance.

I'm not trying to no-true-Scotsman birth control methods, just pointing out that it's hard to draw meaningful conclusions when all you have is people's word.