Now, five years on, he says the “depressing” hypothesis is playing out. In the spring of 2013, there were 19,105,651 students enrolled in higher ed; this spring, there were 17,839,330, according to recently released data from the National Center for Education Statistics. That represents a roughly 7-percent decrease—and is driven largely by declining enrollments in the for-profit and community-college sectors, as well as stagnant enrollments among four-year non-profit public and private institutions. And the trend of declining enrollment in higher education is likely to continue, he argues, for a couple of reasons, but most notably, a declining birth rate means that there will be fewer 18-year-olds entering academe, and there are fewer international and immigrant students to fill those seats.

Why is the dip in enrollment such a big deal? Well, quite plainly, the business model for a lot of colleges is dependent on enrollment. If enrollments decline, revenues decline, and colleges have less money for facilities, faculty, and programs. That creates a sort of death spiral in which colleges are getting rid of programs, which in turn makes it harder to attract students, and so on. For non-selective private liberal-arts colleges, this could mean mergers or closures—something that’s already happening in quite a few places, such as at Marylhurst University in Oregon, Wheelock College in Massachusetts, and St. Gregory’s University in Oklahoma. And for other institutions, Alexander told me in a recent interview, it could mean a shifting of institutional priorities—particularly in the students they recruit and teach, moving away from a primary focus on 18-to-22-year-olds towards more adult learners, as administrators at the University of Memphis have done in Tennessee.

Declining enrollments could also mean the decline of research faculty, increased workloads, and more rapid adjunctification. And given how colleges have treated adjunct faculty, Alexander says, “it would be a humanitarian disaster”—one of higher education’s own doing. “We’ve done it to ourselves with open eyes since the 1990s. And we know about it, it’s kind of an open secret,” he says. “The Research I universities keep pumping out Ph.D.s, and they haven’t slowed down at all. And they know exactly what that means, you know, that the majority of these Ph.D.s are either going to leave academia or end up with horrible labor conditions.”

It’s not a difficult future to imagine—largely because most of it is already happening. Some institutions will be shielded from the decline—most obviously the major players and media darlings such as Ivy League institutions and major public institutions like the University of Texas at Austin. But most colleges will not be so fortunate, he says. They will either have to adapt or die out.