I have been arguing for years that the U.S. has oversold higher education — that many students who attend benefit little from it and will eventually find employment no better than they would have found if they had entered the labor force right after high school.

The Center for College Affordability and Productivity has just released a report that strongly supports my argument. Analyzing data from the Bureau of Labor Statistics on the educational level of individuals working in a great array of jobs, the authors conclude that a large and increasing percentage of college graduates are working in jobs that call for no advanced academic study. They find that “60 percent of the increased college graduate population between 1992 and 2008 ended up in these lower skill jobs.”

The idea pushed by Obama and many in the education establishment is that if we graduate more people from college, all that increased brainpower, skill, and knowledge will make for a more productive labor force. “Investing” more in higher education was supposed to be a way of pulling the economy up by its bootstraps.

It was never a good theory (mere classroom seat time does not necessarily mean useful gains in knowledge) and now we have strong evidence that it is mistaken. Pushing more people through college just means a lot of people with BAs competing with high school graduates for work that only requires on-the-job training.

I suspect that this report, if anything, understates the “underemployment” problem. That is because there are now quite a few jobs that generally exclude high-school graduates not because they couldn’t possibly do the work, but because there are so many college graduates in the labor force that employers can afford to screen out non-graduates. This is the “credential inflation” problem. Restaurant chains, for example, may require that managers have college degrees, but it’s not a job that reasonably intelligent high-school grads couldn’t learn. If it were possible to do an analysis of the labor force that looked only at jobs that require post-secondary education in a knowledge sense (rather than a credential sense), the underemployment percentage would increase greatly.