Roughly (at 4 hours in):

  bachelor's: in the top 75%
  master's:   in the top 33%
  doctorate:  in the top 10%

(I'm assuming that a higher degree is "better", though some would differ. I've heard evidence that startup success inversely correlates with education. Some high-profile anecdotes: Bill Gates doesn't have a bachelors, Woz didn't have one at the time he designed the Apple, and I think the only degrees that Larry and Sergey got were their bachelors).