There is an estimated $730 billion in outstanding federal and private student-loan debt, says Mark Kantrowitz of FinAid, a Web site that tracks financial-aid issues — and only 40% of that debt is actively being repaid. The rest is in default, or in deferment, which means payments and interest are halted, or in forbearance, which means payments are stopped while interest accrues.

(referenced from http://articles.moneycentral.msn.com/CollegeAndFamily/CutCollegeCosts/the-555000-dollar-student-loan-debt.aspx)