I don't think it has been released recently, but given the fact that Penn's overall acceptance rate is 12.3%, and Wharton is more competitive than the other schools, it's safe to say that Wharton's acceptance rate is below 12.3%.
Kafkareborn devised some sort of mathematical model that "uncovered", or at least predicted, the acceptance rate at Wharton. It was a comment in a post linking to a Google Doc, so I don't have it on hand. If he sees this, I'm sure he'll provide it.