All I'm suggesting is the following scenerio.
-->May 15th arrived, and the AdCom at Pitt discovered they were short 20 seats because people withdrew their acceptances. So Pitt had to start offering positions from the waitlist, one group at a time. <--
Now, this poll is only desiged to gain a little insight into how many offers Pitt will need to make to fill their class. e.g if the majority of the people on the waitlist would grab up the offer and hold on to it, then perhaps Pitt would only need to pull 30 people off the list. However, if the majority decline, they may need to offer 60+ acceptances to reach the same result.
I agree with the weakness you point out, boywonder. The poll doesn't ask the people currently holding a Pitt acceptance if they are likely to give it up for another school. I didn't really think to ask that question...probably because at this point I'm expecting most of those holding a seat to not let it go and because it would make this pool to complicated.
Its a good question for another pool, though.