But as the rebound in home prices has slowed in recent months, so has the recovery process for those still submerged with negative equity, according to the latest data from RealtyTrac.
"I'd expect to see this process of digging out of the hole slow down in 2014 because we expect home price appreciation to slow down in 2014," said RealtyTrac vice president Daren Blomquist. "We're already seeing that in the smaller decrease in underwater homeowners over the last quarter."
The pool of underwater borrowers peaked at 12.8 million, or 29 percent of all properties with a mortgage, in the second quarter of 2012, according to RealtyTrac. Rising prices have lifted millions back above water. As of the first quarter of this year, some 9.1 million homes (or 17 percent of homes with mortgages) were "seriously" underwater, owing at least 25 percent more than property's estimated market value.
But the recovery has been very uneven. Like everything else about real estate, location matters a lot.
A look at the county-level data shows a wide range of recovery rates in counties within the same region. In hard hit markets such as Fresno and Stockton, Calif. For example, some 20 to 40 percent of homeowners with a mortgage are still underwater. Not far away, coastal counties such as San Francisco (4 percent underwater) and Orange County (7 percent underwater) have fared much better.
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"Those counties have bounced back much more quickly," said Blomquist. "And that's happening all across the country."
Homeowners in hard-hit states have had the toughest time getting back above water. Those include Nevada, where 34 percent remain seriously underwater, Florida (31 percent), Illinois (30 percent), Michigan (29 percent), and Ohio (27 percent), according to RealtyTrac data.
Hard-hit metro areas include Las Vegas (37 percent seriously underwater), Lakeland, Fla., (36 percent), Palm Bay-Melbourne-Titusville, Fla., (35 percent), Cleveland (35 percent), Akron, Ohio (34 percent), and Detroit (33 percent).
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On the flip side, homeowners in counties with strong home price gains are rapidly building equity. That's likely to help bring more of those homes to market—helping to ease the shortages of homes for sale that have helped drive prices higher in many markets. As those shortages ease, the rate of price increase should continue to slow.