This marketplace for personal data has been a crucial factor in powering the unrivaled lending machine in the United States. European countries, by contrast, have far stricter laws limiting the sale of personal information. Those countries also have far lower per-capita debt levels.

The companies that sell and use such data say they are simply providing a service to people who are likely to need it. But privacy advocates say that buying data dossiers on consumers gives banks an unfair advantage.

“They get people who they know are in trouble, they know are desperate, and they aggressively market a product to them which is not in their best interest,” said Jim Campen, executive director of the Americans for Fairness in Lending, an advocacy group that fights abusive credit and lending practices. “It’s the wrong product at the wrong time.”

Compiling Histories

To knowledgeable consumers, the offers can seem eerily personalized and aimed at pushing them into poor financial decisions.

Like many Americans, Brandon Laroque, a homeowner from Raleigh, N.C., gets many unsolicited letters asking him to refinance from the favorable fixed rate on his home to a riskier variable rate and to take on new, high-rate credit cards.

The offers contain personal details, like the outstanding balance on his mortgage, which lenders can easily obtain from the credit bureaus like Equifax, Experian and TransUnion.

“It almost seems like they are trying to get you into trouble,” he says.

The American information economy has been evolving for decades. Equifax, for example, has been compiling financial histories of consumers for more than a century. Since 1970, use of that data has been regulated by the Federal Trade Commission under the Fair Credit Reporting Act. But Equifax and its rivals started offering new sets of unregulated demographic data over the last decade — not just names, addresses and Social Security numbers of people, but also their marital status, recent births in their family, education history, even the kind of car they own, their television cable service and the magazines they read.