Nearly a quarter of all U.S. home mortgages are under water

There have been a number of attempts to come up with a figure about how many U.S. home mortgages are under water -- in other words, the value of the home loan is more than the value of the house.

All estimates are bound to be wrong because no one has had the time or money to appraise every house in America and match it with the value of its mortgage plus any second mortgages. But The Wall Street Journalhas asked First American CoreLogic, a real estate research company, to give it a try. The report, which is available free online, says that that 23% of mortgages were under water at the end of the third quarter.