It's not exactly that cut and dried that you need OOS people specifically to withdraw, but people in general. UW likes to keep the numbers of accepted students close to the final number, because we can't accomodate more students than 168 or whatever it is now. We really can't, the lecture and small groups are getting pretty full, it's sometimes hard to get a seat in the small group rooms when there's things the whole class has to be there for. That means when someone withdraws, the admissions people will give one of the people who is #1 on one of the waitlists an acceptance. I think there is a limit on the number of OOS students that we can possibly have in the class (it's in the 30s) so they probably want to get below that before they accept any more OOS though. I think we're mandated by the state that we have to have 80% IS but I could be wrong about the exact number.