Nationally, enrollment peaked at 3.4 million in 2010-11 and is expected to bottom out in 2013-14 at about 190,000 fewer, according to the Western Interstate Commission for Higher Education. Pennsylvania is expected to be down about 14,000 by the time the number reaches its nadir.
But that's not the only factor. An improving economy that has sent more people back to work rather than into the classroom also has contributed, in addition to increasing concerns about the cost of college that have led some to postpone school or attend community college and live at home, officials said.
"It is a harmonic convergence in a kind of negative way, I'm afraid," said Mike Reilly, executive director of the American Association of Collegiate Registrars and Admissions Officers.
Schools with more narrow draws, such as public universities, and less selective, small private colleges are most at risk, he said.
To be sure, not all universities are declining. In New Jersey, which has fewer higher education options, enrollment is up at half of the state schools, said Paul R. Shelly, a spokesman for the New Jersey Association of State Colleges and Universities. In Philadelphia, Temple University welcomed its largest class since the recession began.
But Pennsylvania's system has been hit particularly hard, in part because of declining-to-flat state funding. The drop has caused universities, some facing deficits, to rethink programs and operations, said system spokesman Kenn Marshall.
"The ultimate goal is to make sure all of our universities are offering an appropriate array of programs. That may mean eliminating some programs, but it may mean creating some new ones."
A heightened sense of competition is expected.
"Obviously, with everyone competing for a smaller pool of students, everyone is trying to step up their game to try to beat that demographic shift," said Jeff Hileman, a spokesman for Edinboro University, a Western Pennsylvania school that has weathered one of the largest declines - 18 percent - since 2010.
Edinboro repurposed its admissions staff from application processors to aggressive recruiters with territories and quotas, he said. The school also is expanding popular programs, including nursing.
In addition, Edinboro has proposed phasing out five programs as students graduate: philosophy, German, world languages and cultures, music, and music education, he said. A layoff of 41 tenured and temporary faculty is possible.
"It's a painful and difficult situation for the university," he said.
Seven of the universities - Edinboro, East Stroudsburg, Slippery Rock, Cheyney, Kutztown, Clarion, and Mansfield - sent letters to the faculty union in August, saying they were considering layoffs.
The union blames the system for not having foreseen the enrollment drop, union spokeswoman Lauren Gutshall said. The universities should look at other areas, including debt load for new buildings, she said.
"There seems to be some concern that they are more focused on buildings and less on instruction," she said.
East Stroudsburg, which has had a nearly 14 percent student drop since 2010, is evaluating 12 academic departments for reduction in courses, degree concentrations, and faculty, spokeswoman Brenda Friday said.
"A lot of things will be determined based on how we do with enrollment this year," she said.
To raise enrollment, East Stroudsburg created an office to bring in more transfer students.
Kutztown in Berks County opened a division of enrollment management.
Clarion, in Western Pennsylvania, is considering cutting 54 faculty - 40 through layoffs. It's also looking at phasing out music education and secondary education in French, spokesman David Love said. The university faces a $12 million deficit.
Mansfield, with a projected deficit of $14.3 million, plans to cut 29 faculty and 25 staffers.
Cheyney's enrollment dropped 5.6 percent this year, spokeswoman Gwen Owens said. Cheyney, a historically black university, faces a $14 million deficit. The enrollment decline is due in part to less available federal aid for students, she said. Cheyney hasn't decided on layoffs.
At nearby West Chester, enrollment is up 2.8 percent, spokeswoman Pam Sheridan said. West Chester has increased retention of students and recruited more heavily out of state, in Virginia, Long Island, and New Jersey, she said.
"Probably the biggest marketing tool is a rejection letter," Sheridan said. "The more selective we become, the more popular we become."