rhyme
I've wondered what the percentages jump to... In my head I like to think that a whole ton of people get thrown out before the interview process, and those that make it past have a 50% chance.
I'm going to keep my head buried in the sand and run with this totally unsubstantiated perception.

rhyme, your understanding is correct....Based on my interaction with current students at Wharton and recent alumni, Wharton usually offers admission to 50% of its interviewed applicants…..However, some of them end up going some where else (I am sure that you know the name of those two schools where these folks end up going)
According to Sandy at the BW forum, Wharton offers admission to about 1/3 of interviewed applicants. There is a current discussion about Wharton admissions going on there.