Homes in the United States have lost trillions of dollars in value during 2008, real estate website Zillow.com said. The report came as nearly 11.7 million American households now owe more on their mortgage than their homes are worth. U.S. homes are set to lose well over $2 trillion in value during 2008, according to an analysis of recent Zillow Real Estate Market Reports. Home values declined 8.4 percent year-over-year during the first three quarters of this year, compared to the same period in 2007, the reports showed. U.S. home values lost $1.9 trillion from the first of 2008 through the end of the third quarter, and will probably fall further in the fourth quarter. One in seven of all homeowners, or 14.3 percent, were “underwater” by the end of the third quarter, the reports showed. “In general, homeowners in most areas we cover are struggling with foreclosures pouring into the market, large amounts of negative equity and dropping home values. On the positive side, in the third quarter, some markets—particularly those hit hardest in the downturn—showed smaller year-over-year declines than in the prior quarter,” Doctor Stan Humphries, Zillow's vice president of data and analytics, said in a statement. “Our optimism here, though, must be tempered by the knowledge that the larger economic problems that emerged in the fourth quarter will likely further challenge the real estate market,” he said. The U.S. housing market is suffering the worst downturn since the Great Depression as a huge supply of unsold homes, tighter lending standards and record foreclosures push down home prices.