Nearly 2 million U.S. homeowners escaped negative equity in their homes in 2012 because of rising house prices, and 1 million more will enjoy the same development this year, according to real estate publisher Zillow.

Zillow’s quarterly Negative Equity Report showed the percentage of homeowners with a mortgage underwater fell to 27.5 percent at the end of 2012, down from 31.1 percent at the end of 2011.

Zillow Chief Economist Stan Humphries said that as the trend grows, there would be numerous positive effects for the housing market.

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“Freed from negative equity, homeowners will have more flexibility, and some will likely choose to list their home for sale, helping to ease inventory constraints and moderating sometimes dramatic, demand-driven price increases in some markets,” Humphries said.

Among the nation’s 30 largest metro areas, those with the highest number of homeowners freed from negative equity in 2012 were Phoenix, Los Angeles, Miami-Fort Lauderdale, Dallas-Fort Worth and Riverside, Calif.

However, 13.8 million Americans are still struggling with negative equity, Zillow said.

The drop in negative equity was largely due to a 5.9 percent increase in home values nationwide last year to a median Zillow value of $157,400.

In a similarly optimistic note, the National Association of Realtors (NAR) reported existing-home sales edged up in January, and that a “seller’s market” is developing as home prices continue to rise steadily.

Sales rose in every region but the West, which is the region most constrained by limited inventory, the NAR said.

Lawrence Yun, NAR’s chief economist, said tight inventory is a major factor in the market.

“We expect a seasonal rise of inventory this spring, but it may be insufficient to avoid more frequent incidences of multiple bidding and faster-than-normal price growth,” he said.

The NAR reported total existing-home sales increased 0.4 percent to a seasonally adjusted annual rate of 4.92 million in January from a downwardly revised 4.90 million in December, and are 9.1 percent above the 4.51 million-unit pace in January 2012.

Distressed homes — defined as foreclosures and short sales — accounted for 23 percent of January sales, down from 24 percent in December and 35 percent in January 2012. Fourteen percent of January sales were foreclosures and 9 percent were short sales, according to the NAR.

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