Private student loans, which are found to be more risky and expensive than federal loans, accounted for one-fifth of the amount of debt students owed.

As students pile on more debt, they are also having a harder time repaying it. The percentage of borrowers who defaulted on their federal student loans within two years of their first payment jumped from 8.8% to 9.1% in fiscal year 2011, the U.S. Department of Education reported earlier this month.