To clarify this again -
What happened the last 3 years (current junior, soph, freshman classes) at UM is that they accepted their usual "30 to yield 20." In each of these years, nearly all of those who were admitted accepted. (29 of 30 in the class of 2007, for example). They have accepted the same number of students each year; they have not changed that, although it has been rumored (for the past 2 years) that they will. It may be true that they have deferred more than usual early on because of this phenomenon of "no one saying no," but it may also not be true - only Brent Wagner knows for sure!
