WASHINGTON — The big question is: How bad will it get?

So far, the rising mortgage defaults that panicked markets this week have been concentrated in areas of the country already reeling from layoffs in the automobile industry and in hurricane-stricken states on the Gulf Coast.

In Mississippi and Louisiana, about 1 in 10 homeowners are failing to make their payments, fresh data show. Ohio, Michigan and Indiana, the nation's industrial heartland and the states suffering the country's highest unemployment, aren't far behind.

Yet the repayment of mortgages is holding up well on the Atlantic and Pacific coasts and in other parts of the country, including those that saw huge run-ups in property values in recent years.

Not only that, but there is scant evidence — so far — that the mortgage problems are causing wider economic damage. But the big worry, on Wall Street and on Main Street, is that the trouble will spread, worsening the downturn in the housing market and possibly tipping the economy into a painful recession.

"The question now is whether the pathology of the housing market is going to infect the rest of the economy," said Edward Leamer, director of the Anderson Forecast at the University of California-Los Angeles. "We're optimistic about the economy ... (but) it's going to feel like a depression in the housing sector."

A few economic Cassandras have been warning for more than a year that the mortgage market was ripe for trouble that could take down the whole economy. They've not yet been proven right, but in recent weeks they have been looking a lot smarter.

"The tragedy of the current situation is that it was entirely predictable," said John Vogel, a professor at the Tuck School of Business at Dartmouth College.

"What's surprising is how fast this is unraveling," he said. "Mortgage brokers pushed exotic mortgage products that allowed people to buy houses that only made sense if prices kept rising. Now that houses have stopped appreciating, people are going to lose their homes and their savings."

A major sign that broader trouble could be brewing emerged Tuesday after a national survey by the Mortgage Bankers Association showed a soaring number of homeowners failing to make their mortgage payments in the last three months of 2006. The group also reported that foreclosures on all homes leaped to the highest level in nearly four decades.

That news sent every major stock-market index plummeting as soon as it was released.

A deeper look at the survey reveals a tale of two Americas.

In many parts of the country, housing prices skyrocketed beyond income growth over the past few years. Millions of people, wanting to get a piece of the action, got risky types of mortgages to finance a home-buying splurge that was beyond their means.

These areas have seen home prices slip from their soaring highs over the past year, but homeowners do not seem to be facing economic crises, analysts said. In Virginia, for example, which had rapid job growth and relatively low unemployment, delinquency and foreclosure rates were less than the national rates, the report showed.

For those living in economically hard-hit areas, including the Gulf states and the industrial heartland, where the auto industry is still a dominant force, getting a loan from banks that specialize in "subprime," or risky, mortgages was not an investment play or a way to get into an expensive home. It was often a matter of keeping families afloat as money got tight.

After hurricanes Katrina and Rita hit the coast in 2005, "people took lines of credit for household expenses, people took on additional debt to maintain their businesses. They needed cash to keep on living," said Andrew Kopplin, executive director of the Louisiana Recovery Authority. "Struggling under one note is tough. Struggling under two notes is impossible. But that's what they face."

Now, as the market for the riskiest types of loans collapses, the homeowners holding such mortgages are the most likely to lose their homes, economists said. Whether the most troubled states are outliers or a sign of what is to come for the rest of the country will depend on whether the nation's deepening housing slump leads to broad job losses, analysts said.

While home-building and related industries are likely to shed more workers this year, most economists, including those at the Federal Reserve, have forecast that the economy will keep growing, albeit sluggishly, propelled by job growth in healthcare, education, finance and other services.

There was little doubt, however, than an influx of homes from foreclosures would have an impact on housing prices, which are already down.

Analysts at Lehman Brothers said that it would take several months for the rising number of foreclosures to translate into a higher supply of homes on the market. Their early estimates show that the inventory of homes may rise by 300,000 in 2008 and 400,000 in 2009.

That represents only a small portion of the 7.5 million homes that are bought and sold every year, but analysts say it is enough to add psychological pressure in an already nervous housing market. Moreover, the added inventory could have a disproportionate impact in some markets where supply already exceeds demand.

"Inventory levels already are at record highs," said Michelle Meyer, a Lehman Brothers economist. "So if you add to the large supply of homes, the market will take longer to correct." Meanwhile, some banks and other institutions may have to bear the pain of the meltdown in subprime mortgages.

The government-chartered Fannie Mae and Freddie Mac, two of the nation's largest investors in mortgages traded on the bond market, have limited their bets in the subprime category so that they face only a remote possibility of significant losses, said Corinne Russell, spokeswoman for the Office of Federal Housing Enterprise Oversight, a regulatory agency.