Rising home prices have lifted more and more homeowners out of negative equity, according to a report released Thursday by Zillow.

The number of homeowners with mortgages who owe more than their home is worth is down to 28.2 percent across the country, marking the first time it has fallen below 30 percent since the real estate Web site began tracking the data in the first quarter of 2011.  

In the Washington region, the number of underwater homeowners dropped to 28.5 percent from 31.3 percent in the second quarter, the largest quarterly decline (2.8 percent) in almost two years.

Zillow partnered with credit bureau TransUnion to determine the mortgage balances on homes and then paired that information with estimates of the home’s values to calculate how many homeowners have negative equity.

More than 14 million homeowners nationally owed more than their homes were worth in the third quarter.

Young people appear excessively affected by negative equity. Close to 44 percent of borrowers younger than 40 were underwater in the third quarter.

Although 321,264 homeowners in the Washington region were underwater in the third quarter, that number has been trending downward this year. It represented a decrease of 31,567 from the second quarter and 43,935 from the first three months of the year.

Of those who have negative equity in this area, 38.2 percent are underwater by 20 percent or less.  

Compared to the other 30 metro areas tracked by Zillow, Washington falls about in the middle. The region is not doing nearly as well as Pittsburgh, where only 14.3 percent of homeowners owe more than their home is worth, or Boston (17.5 percent). But it is doing much better than Las Vegas, where two-thirds of homeowners are underwater, and Atlanta, where more than half of homeowners have negative equity.

Prince George’s County, which suffered the brunt of the housing recession in this region, showed signs of improvement in the third quarter. Even though more than half the homeowners (54.3 percent) are underwater, the number who owe more than twice what their homes are worth fell to 17.9 percent from 20 percent three months earlier.  

Another county hard hit by the downturn, Prince William, also gained ground. The number of homeowners with negative equity dropped to 32.2 percent from 36.8 percent between the second and third quarters.

While negative equity remains a significant issue in those two counties, it is much less so in Fairfax and Montgomery counties. Fewer than 10 percent of the homeowners in Fairfax cities such as Great Falls (7 percent), Vienna (7.8 percent), McLean (8 percent) and Dunn Loring (9 percent) owe more than their homes are worth.  

The same goes for Montgomery County, where fewer than 10 percent of the homeowners in Glen Echo (4 percent), Potomac (5 percent), Cabin John (5.9 percent) and Bethesda (9.1 percent) are underwater.

This report is good news for a local housing market that has been plagued by low inventory. The supply of homes for sale has reached historic lows as homeowners have been stuck in homes they bought at or near the peak of the market.  

Lawrence Yun, chief economist for the National Association of Realtors, said even though the housing stock may turn over it won’t necessarily improve the inventory problem. He pointed out that underwater homeowners who are able to sell are going to be buying another home, putting one property on the market, but taking another one off.

“So it will be a net wash,” he said. “It will not really relieve the inventory situation even though the transaction volume may be rising. The only way to genuinely relieve the inventory situation is really for the homebuilders to add more homes to the marketplace.”

According to Yun, one of the biggest gains from fewer homeowners owing more than their homes are worth is that not as many will be tempted to walk away from their homes.

“That is a great motivator for people not to strategically default,” Yun said. “When prices were continuing to fall, that was a highly demoralizing situation where even if the person has the capacity to pay, they may just give up and say to heck with it. But rising prices will reduce strategic default thinking among homeowners.”

Zillow chief economist Stan Humphries cautioned, however, that these improvements could be short-lived if the budget crisis is not resolved before January.  

“While we’re moving in the right direction, a substantial number of homes are still locked up in negative equity, unable to enter the existing re-sale market despite the desires of their owner,” he said in a statement. “The housing market has found real momentum of its own, but is not immune from shocks to the broader economy. If negotiations centered on resolving the fiscal cliff don’t inspire confidence in investors and consumers alike, recent home value gains — and, as a result, falling negative equity rates — could stall.”