I didn’t try to find that out, it’s, as you say, impossible to find out. Triple stumpers set an upper boundary for the humans, the theoretical maximum. That’s what I calculated. About three triple stumpers per round seem to be the norm, even among the best, that puts the upper boundary – the theoretical maximum – at 90%. The humans might still be worse than 90% but they are definitely not better (when there are three triple stumpers).