What does a university do if too many accepted students enroll?
Have bigger classes, bunk three to a room.
They contact all admitted students to see if anyone is willing to take a gap year or delay matriculation until the 2nd semester. Contract for off campus housing.
Even more importantly, they admit less the following year.
First, they would not admit any from the waitlist. Second, they need to have larger classes or more classes. Third, they may need to find enough dorm rooms for freshmen.
It happened to UMich quite often and particularly 2 years ago. They were short of 300 beds. They ended up renting luxury apartments around campus for return students to trade for their dorm spaces with no extra cost. I think they really got burnt that time and decided to admit less students.
If it were SUNY…celebrate is my guess.
I am still amazed that the colleges have this figured out for the most part.
They are pretty good and figuring it out these days. But, in the mid-1980s, my sister went to BC where they had just had a good football season. The yield was so high her freshman year that many students were housed 3 to a 2 person room. It was very snug!
For most schools, the yield rate would not change too much and they usually have the waitlist as backup plan. For UMich, they did not use much the waitlist previously while the yield rate went up ~0.5% per year in the decade or so and then it jumped up 2% (5% change) 2 years ago which led to 5% more than expected students.