A new study suggests that rising tuition costs, higher borrowing limits on government loans and new wave of low-income students have pushed average debt burden of college graduates higher as more students borrow. Undergraduate students borrowed, on average $19,300 which is up from $12,100 a decade earlier. More students, even from the nation's wealthiest families, took on debt to pay for college. The volume of federal government loans alone rose 137 percent from 1992 to 2002, to $20.7 billion.