More than half of all home­owners with mortgages in the Tampa Bay area owe more than their property's worth.

The latest troubling news on "underwater" mortgages emphasizes how real estate could remain a stickler even as the overall economy improves.

First American CoreLogic said 50.6 percent of Tampa Bay residential mortgages, worth $59.3 billion, were upside-down as of June 30. That comes to about 351,980 mortgages out of roughly 700,000 in the region.

In Florida as a whole, 2.3 million out of 4.7 million mortgage borrowers - or 49.4 percent - had negative equity.

In March, First American reported that 31 percent of Tampa Bay homeowners were underwater, but the rise since then is deceptive. The company said it has changed its methodology to include more second mortgages. Counting that extra housing debt shoved more homeowners into negative equity territory.

"Negative equity continues to be the dominant driver of the mortgage market because it leads to foreclosures in the event a borrower experiences some kind of economic shock: job loss, illness or other adverse situation," said First American economist Mark Fleming.