Does this make sense? The number might be slightly off...(I wrote this to my mom...)
Michigan has offered, thus far, between 310-320 students a spot for their 2006 class. Historically, Michigan ends up offering between 375 - 425 total positions for each academic year (I'm not sure how entirely accurate those numbers are, but I'm close) for a class size of 170.
Last year, at this same time, Michigan made offers to about 375 students. Because so many candidates wanted to go to Michigan, Michigan never went below the 170 threshold and thus never dipped into their waitlist. Last year was an abberation; in years previous to last year Michigan would accept 375 students and then take additional students off the waitlist, perhaps offering admissions up to 425 total candidates.
Because Michigan had more students than they wanted for 2005, this year Michigan is exercising more caution. They are accepting fewer students up front, then as withdrawals come in AND as they dip below 170, they will give admissions offers to students off the waitlist.
If you believe in empirical evidence and trends, Michigan will be handing out, at a minimum, 50 more offers this year. It might be as high as 75 or 100.