Young Americans with big college debts are often portrayed as struggling to pay their bills. The reality is somewhat different -- those owing super-sized student loans tend to be higher paid.

A Reuters analysis of Federal Reserve data shows that over the past two decades the young with higher incomes have gone from owing less of the debt than the average household to owing considerably more.

U.S. student loan balances have quadrupled since 2004 to $1.1 trillion, prompting credit rating agency Standard & Poor's and others to express fears the borrowing could crimp consumer spending, especially home buying, and eventually lead to the painful bursting of a bubble. Worries over high loan levels have also been voiced by President Barack Obama and more recently, Federal Reserve Chair Janet Yellen.

Without doubt, many families struggle to pay the rising costs of college, and high levels of unemployment have only added to the distress. Delinquency rates on student loans remain well above historically average levels.

But the analysis of the Federal Reserve's Survey of Consumer Finances, a triennial survey published in September with 2013 data, makes it clear that heavy borrowing is usually rewarded with big salaries. The increased concentration of debt among the well-paid should ease concerns that the surge in debt is a wider economic threat.

The data show that most of the nation's overall loan balances are held by those earning more than $60,000. Moreover, among households that owed at least $60,000 and were young, defined as those headed by someone between 20 and 40 years of age, average income last year was $82,000.