Lonnie Briglia, 60, lost his home in Fort Pierce, Fla., to foreclosure. (Michael S. Williamson/The Washington Post)

There's a popular theory of what caused the 2007-2008 housing crisis that goes something like this: The problem started when greedy bankers gave poor people loans to buy houses that lenders knew they couldn't afford.

That enabled more people to bid on homes, driving up prices, according to this version of events. Then, when poor borrowers were not able to pay their bills, banks stopped issuing new mortgages. The number of buyers dwindled, prices plummeted and the bust began. Homeowners were underwater across the country, and major banks were left with foreclosed houses that were essentially worthless as collateral.

It is a story that has been told about the crisis again and again by Republicans, Democrats, economists, journalists and filmmakers. The movie “The Big Short,” based on the book by Michael Lewis, is all about so-called subprime loans — risky and often complicated mortgages that were frequently sold to less affluent homeowners.

Yet many economists argue this story is misleading. In a new paper, one group of researchers argues that these accounts put a disproportionate amount of blame on borrowing by the poor. In reality, they say, it was home loans to all kinds of borrowers that inflated the catastrophic housing bubble.

Specifically, they point out that lending increased not only to poor consumers but for Americans regardless of their incomes. In particular, the paper shows that the share of Americans owning homes increased the most among the well off, while that share actually declined among the poor.

“The boom happened for everyone. It was not primarily a boom for the low-income households,” said Duke University's Manuel Adelino, who wrote the paper along with Antoinette Schoar of the Massachusetts Institute of Technology and Dartmouth College's Felipe Severino.

The subprime lending to less affluent homeowners could have made a bad situation worse, but those loans cannot explain the rush on housing throughout the entire industry, according to the three economists, whose working paper published this week by the National Bureau of Economic Research.

Their paper is the latest in a series challenging the popular view of the crisis. Last year, a group of economists from the Federal Reserve Bank of Boston came to similar conclusions.

Yet many experts are still unconvinced. They ask why housing prices rose so rapidly if subprime loans were not the cause — and the revisionists do not have a complete theory of their own. In short, nearly a decade after the implosion of the national housing market began, there is still little consensus among economists about why it all came apart.

“We don't have a good explanation,” Adelino said. “I don’t want to be making up a reason for why house prices are going up or down.”

That is a problem for policymakers, who are still debating how best to respond to the crisis — and keep a similar one from cratering the economy in the future. Last week, House Republicans approved a bill that would overhaul the country's financial sector, undoing the reforms Democrats enacted in the Dodd-Frank law of 2010.

The rich and the middle class

Wealthy Americans have always been more likely to own homes. Among the richest household in every five, 87 percent owned homes in 2000, before the boom began in earnest. The national average for that year was just 66 percent.

During the run-up in housing prices, however, that figure rose even higher, increasing 2.7 percentage points by 2005, according to Adelino and his colleagues. The increase was less pronounced for the middle class. Among the 20 percent of households in the center of the distribution of income, the rate of homeownership among typical households rose just 1.6 percentage points in those five years.

Meanwhile, homeownership in fact declined among the poor. Among the poorest 20 percent of households, the share owning homes fell 0.6 percentage points over that period.

It was not just that wealthier households were better able to afford those new mortgages. On average, wealthier households borrow less relative to their incomes. As the boom accelerated, though, the rich began receiving riskier loans as well, Adelino, Schoar and Severino's paper shows. Average mortgage debt as a share of income increased in tandem for rich, poor and middle-class households alike during the boom.

More affluent homeowners also started getting into trouble more. In 2003, just about 33 percent of all delinquent mortgage debt was owed on homes in the richest 40 percent of Zip codes. By 2006, that figure increased to 41 percent, the authors note.

The problem with subprime

Banks were taking bigger risks on affluent borrowers as well as on the poor. All the same, many observers argue that subprime loans along with other unconventional financial products might have been particularly problematic.

Many prime loans were insured by Fannie Mae and Freddie Mac, which absorbed the losses associated with those mortgages when they went bad. By contrast, subprime loans were issued by the private sector, which frequently resold them to other firms, sometimes without revealing all the risks involved.

When those mortgages failed, those buyers found themselves in financial trouble. Worse, the complexity of the products made it difficult for the buyers to figure out just how deep in the red they were, said David Fiderer, a former investment banker at Crédit Agricole and an expert on housing policy. That uncertainty resulted in a panic, he said.

“It’s hard to evaluate the mortgage crisis without really looking at the incidence of fraud,” Fiderer said, pointing to a series of legal actions brought by governments against financial institutions. “It was prevalent, almost ubiquitous.”

Who's to blame

Banks did not only issue subprime mortgages to the poor, however. Better-off borrowers used these products as well, along with other unconventional loans such as the so-called Alt-A mortgages, which were another source of instability.

The debate over all these minutiae of the previous decade's housing market is not just about what caused the crisis. At some level, it is also a debate about who caused the crisis. That is the kind of argument that can get heated in a hurry.

Many Americans — rich and poor, on Wall Street and on Main Street — were infected with a dangerously unjustified enthusiasm for mortgages. Yet some experts argue that bankers actively bent the rules in a cynical and shortsighted effort to make money at the expense of ordinary Americans, and that they wrongly escaped punishment when the crash came. From that point of view, financiers should not be able to defend themselves on the grounds that the housing bubble was simply an episode of collective insanity.

Setting aside the question of the banking sector's culpability, one clear conclusion from the new paper seems to be that too much blame has been assigned to the poor. More affluent households borrowed excessively as well, and many of them also relied on dangerous unconventional loans.

After the crisis, banks withdrew credit abruptly from low-income clients. As a result, the rate of homeownership among the poor declined even further, from 43 percent in 2000 to 39 percent in 2015, Adelino and his colleagues write. Homeownership among better off households has also declined, but less so.

Pushing so many poor would-be homeowners from the market might not have improved the overall stability of the housing sector, Adelino said. On the other hand, Americans have long regarded an investment in a home as the way to establish a comfortable, middle-class standard of living.

“The burden of the reduction in credit was borne — I think, in that case, disproportionately — by low-income households,” he said.

“There’s a lot of class bigotry involved,” Fiderer said. “People think, 'Oh, well, what happened was people who shouldn’t have bought homes bought homes because of easy credit, and that’s what happened.'”