"The median earnings of full-time workers with bachelor’s degrees was nearly $47,000 in 2007, according to the Census Bureau. The median for someone who had attended college but failed to get a four-year degree was nearly $33,000, and the median for a high-school graduate was nearly $27,000. Compare these numbers with the typical education debt that a college student has on graduation day — $20,000 — and it’s clear that a college education is worth the debt."
"One well-known study, co-written by Alan Krueger... offered some support for the skeptics. It tracked top high-school students through their 30s and found that their alma maters had little impact on their earnings. Students who got into both, say, the University of Pennsylvania and Penn State made roughly the same amount of money, regardless of which they chose."
Other studies come to different conclusions:
"Several studies have found a large earnings gap between more- and less-educated identical twins. Another study compared young men who happened to live close to a college with young men who did not. The two groups were similar except for how easy it was for them to get to school, and the upshot was that the additional education attained by the first group lifted their earnings. “College can’t guarantee anybody a good life,” says Michael McPherson, an economist who runs the Spencer Foundation in Chicago, which finances education research. “But it sure ups the odds substantially.”"
Just to show the issue is not fully settled:
"Yet the skeptics do make one crucial point. Nationwide, half of all students who start college don’t end up with a four-year degree. Not only do these dropouts spend less time in class, but they also miss out on the signalling benefit of the degree — a mark of those who, among other things, have the discipline to finish what they start."