The American political class has long held that higher education is vital to individual and national success. The Obama administration has dubbed college "the ticket to the middle class," and political leaders from Education Secretary Arne Duncan to Federal Reserve Chairman Ben Bernanke have hailed higher education as the best way to improve economic opportunity. Parents and high-school guidance counselors tend to agree.

Yet despite such exhortations, total college enrollment has fallen by 1.5% since 2012. What's...