About 8.31 million properties had negative equity at the end of 2008, up 9 percent from 7.63 million at the end of September, according to the study, released today by First American CoreLogic. The percentage of “underwater” borrowers rose to 20 percent from 18 percent.

Another 2.16 million properties could go underwater if home prices fall another 5 percent, the study shows.

First American said the value of residential properties fell to $19.1 trillion at year-end from $21.5 trillion a year earlier, with half the decline in California. Forty-three U.S. states and Washington, D.C., were included in the study.

While states such as California, Florida and Nevada were particularly stressed, the study showed worrying signs of deterioration in relatively healthy parts of the nation.

Arizona, California, Florida, Georgia, Michigan, Nevada and Ohio remained the most stressed states, with 62 percent of underwater borrowers and just 41 percent of mortgages.

Other areas, though, also face more stress. Connecticut, for example, saw a 25 percent increase in homes with negative equity, while Washington, D.C., had a 44 percent increase.

Roughly 68 percent of U.S. adults own their own homes, and about two-thirds of these have mortgages. Many economists expect the nation’s unemployment rate to rise above 9 percent before the recession ends, up from January’s 7.6 percent.

California had 1.9 million borrowers with negative equity at year-end, more than any other state, followed by Florida’s 1.28 million. About three in 10 borrowers in both states were underwater.

By other measures, Nevada was the most stressed, with 55 percent of owners having negative equity and borrowers on average owing 97 percent of what their homes are worth. About 28 percent owe more than 125 percent of their homes’ value.

Michigan had 40 percent of its homeowners underwater, while Arizona had 32 percent.

New York fared best, with just 4.7 percent of borrowers with negative equity and an average 48 percent loan-to-value ratio, though this could change as employment and bonuses slide in the financial services industry.

According to the S&P/Case-Shiller Home Price Indices, prices of U.S. single-family homes slumped 18.5 percent in December from a year earlier, the biggest drop in the 21-year history of the data.

Many lenders are taking steps to keep borrowers out of foreclosure. The Obama administration has backed legislation that could broaden powers of bankruptcy judges to modify mortgages for troubled borrowers. Among major lenders, only Citigroup Inc has supported such a plan.

A forbearance agreement is an arrangement made between a creditor and its lenders to postpone, reduce or suspend payment due on a loan for a limited and specific time period.

Station Casinos had said it may have to file for bankruptcy protection if agreements could not be reached with its lenders.

The Las Vegas-based company owns, operates and manages casinos in Las Vegas, geared primarily for the local community.

The forbearance agreements with the holders of the old senior and senior subordinated notes and the lenders under its previous credit agreement dated Nov. 7, will expire on April 15, the company said in a statement.

Like many casino operators, Boyd has been squeezed as consumers tighten their discretionary spending due to mounting economic and job concerns.

For the period ended Dec. 31, the casino operator reported a loss of $2.51 per share, reversing net income of $31.2 million, or 35 cents per share, reported a year earlier a year earlier.

Quarterly results included $290.2 million in impairment charges, which were taken to write down some acquisitions to account for their fair value as of Dec. 31.

On Monday, the casino operator informed Station Casinos Inc. that it is interested in acquiring the struggling gaming operator’s assets after, or as part of, a bankruptcy reorganization.

Revenue from Las Vegas locals properties, or casinos frequently mostly by residents of the region, fell to $176.8 million from $214.4 million. Downtown Las Vegas revenue slipped to $60.8 million from $66.9 million, while revenue from sites in the Midwest and South declined to $185.1 million from $197.3 million.

Boyd posted a full-year loss of $223 million, or $2.54 per share, compared with a profit of $303 million, or $3.42 per share, in the prior year. Annual revenue fell to $1.78 billion from $2 billion a year earlier.

The loss Wynn reported after the market closed compares with net income of $65.5 million in the fourth quarter of 2007. Wynn said it lost $1.49 per basic share during the last three months of 2008 compared with income of 58 cents per share a year earlier.

The company, which owns casinos in Las Vegas and the Chinese gambling enclave of Macau, said the large tax expense resulted from a company review of its ability to realize future tax benefits.

For the full year, the Las Vegas-based company says its net income was $210.2 million, or $1.94 per basic share, compared with $258.1 million, or $2.43 per share in 2007.

Wynn says its gambling revenue for 2008 was $479.7 million, 25.3 percent less than in 2007. Non-gambling revenue was $776.3 million in 2008, down 3.7 percent from 2007.

The company said in a conference call with investors that it learned in the fourth quarter that it could not keep its room rates high and expect its Las Vegas hotels to remain full.

The company, which opened the $2.3 billion Encore Las Vegas resort on Dec. 22, said the opening did not significantly affect results for the fourth quarter. Wynn Resorts said it had $202 million in outstanding costs for the project.

Wynn Resorts said it plans to open the $700 million Encore Macau casino in 2010, with 400 luxury suites and four villas. The company said it planned to fund the project with cash on hand and revenue from Wynn Macau.

The company said it had $1.1 billion cash on hand at the end of 2008 and $4.3 billion in total debt.