HIGHER EDUCATION BUBBLE UPDATE: Low-Paid Grads Not Spending Money Or Building Careers.

Underemployment isn’t debilitating only for individuals whose career and income opportunities are stunted. It threatens the economic expansion as college-educated young adults have traditionally fueled consumer spending on clothes, technology, entertainment and cars.

“If you have a stumbling entry into the labor market, you risk getting stuck in jobs for which you’re overqualified and poorly paid for the rest of your life,” said Katherine Newman, a sociologist and dean of the school of arts and sciences at Johns Hopkins University in Baltimore who has studied the long- term effects of underemployment. “There’s a scarring effect, with employers you want marking you as undesirable. The economic toll is enormous.”

The underemployed include those of all ages who are working part-time but want full-time positions. There were 8.2 million people working part-time for economic reasons in June, according to the U.S. Bureau of Labor Statistics. That number had doubled to 9.1 million in the last quarter of 2009 from 4.5 million in the same period of 2007.

It’s not pretty.