In her Washington Post column Catherine Rampell correctly pointed out that the median return in higher wages for those with college degrees more than covers the tuition and opportunity cost associated with attending college. She notes however that college enrollment has edged downward in recent years.
While she sees this decline largely as the result of young people failing to recognize the benefits of college, it can be more readily explained by a growing divergence in the income of college grads. Work by my colleague John Schmitt and Heather Boushey shows that a substantial proportion of college grads, especially male college grads, earn less than the average high school grad. They found that the lowest earning quintile of recent college grads (ages 25-34) earned less than the average high school grad. The implication is that many young people may be reasonably assessing their risks of not being a winner among college grads and therefore opting not to get additional education. To get more young people to attend college it is important that most can predictably benefit from the additional education, not just that the average pay of college grads rises. (of course the story would be worse for those who start college and do not finish.)
Note: typos were corrected and the comparison was clarified.