America's college-aged population is declining. Universities will have to make cuts.

As America's population ages and some state populations are expected to decline, demographic shifts may profoundly reshape the country's colleges and universities.

Academics have long worried about the enrollment cliff, a multiyear decline in traditional college-aged students following an anticipated peak in 2025. Although the total number of undergraduate students at America's universities rose steadily from approximately 7.3 million in 1970 to around 18 million in 2010, enrollment has stagnated, with 16.1 million undergraduate students enrolled this past fall, according to the National Cente...