Geroge Leef has staked out a position that college is oversold and that we’re in the midst of a higher education bubble. A new Bloomberg Businessweek article adds more grist to Leef’s mill.

With tuition up more than sixfold in the past three decades—to $32,000-plus for four years at a state university and $83,000 in a private school—the percentage of people with student loans who quit without a degree is on the rise. Almost 30 percent of borrowers who started college in 2003 dropped out within six years, up from 23 percent of those who started in 1995, according to Education Sector, an independent think tank. Borrowers who drop out are four times more likely to default on their loans as those who graduate, the group says. “As long as college prices keep increasing, the tension students face between trying to minimize debt and maximizing their chances of graduating will continue to grow,” says Mary Nguyen, who authored a report on the topic for Education Sector. In 2009, the median income for borrowers who dropped out of college in the previous six years was $25,000, or $5,000 less than those who graduated in those years, Nguyen says.

Roughly 36 million Americans have attended college without earning a degree, says Anthony Carnevale, director of the Georgetown University Center on Education and the Workforce. The median lifetime earnings of someone who gets a bachelor’s degree today will be about $2.3 million, while those with some college but no degree will earn $1.5 million, the center reports. Those with only a high school diploma will make $1.3 million—but likely won’t have student debt. “The worst case is if you go into a low-earning field, don’t graduate, and accumulate debt,” Carnevale says. “In the end, what you get is the debt and no real increase in earning power.”