But behind the big increase in consumer debt is a major shift in the way lenders approach their business. In earlier years, actually being repaid by borrowers was crucial to lenders. Now, because so much consumer debt is packaged into securities and sold to investors, repayment of the loans takes on less importance to those lenders than the fees and charges generated when loans are made.

Lenders have found new ways to squeeze more profit from borrowers. Though prevailing interest rates have fallen to the low single digits in recent years, for example, the rates that credit card issuers routinely charge even borrowers with good credit records have risen, to 19.1 percent last year from 17.7 percent in 2005 — a difference that adds billions of dollars in interest charges annually to credit card bills.

Average late fees rose to $35 in 2007 from less than $13 in 1994, and fees charged when customers exceed their credit limits more than doubled to $26 a month from $11, according to CardWeb, an online publisher of information on payment and credit cards.

Mortgage lenders similarly added or raised fees associated with borrowing to buy a home — like $75 e-mail charges, $100 document preparation costs and $70 courier fees — bringing the average to $700 a mortgage, according to the Department of Housing and Urban Development. These “junk fees” have risen 50 percent in recent years, said Michael A. Kratzer, president of FeeDisclosure.com, a Web site intended to help consumers reduce fees on mortgages.

“Today the focus for lenders is not so much on consumer loans being repaid, but on the loan as a perpetual earning asset,” said Julie L. Williams, chief counsel of the Comptroller of the Currency, in a March 2005 speech that received little notice at the time.

Lenders have been eager to expand their reach. They have honed sophisticated marketing tactics, gathering personal financial data to tailor their pitches. They have spent hundreds of millions of dollars on advertising campaigns that make debt sound desirable and risk-free. The ads are aimed at people who urgently need loans to pay for health care and other necessities.

It is not just financial conglomerates that are profiting on consumer debt loads. Some manufacturers and retailers can generate more income from internal financing arms that lend to their customers than from their primary businesses.