The Federal Reserve says Americans' percentage of equity in their homes has fallen below 50 percent for the first time since 1945.

The Fed's U.S. Flow of Funds Accounts shows homeowners' percentage of home equity slipped to a revised 49.6 percent in the second quarter of 2007 and declined further to 47.9 percent in the fourth quarter. It marks the first time homeowners' debt on their houses exceeds their equity since the Fed started tracking the data in 1945.

Home equity is equal to the percentage of a home's market value minus mortgage-related debt.

On average, housing is Americans' single largest asset. Economists expect falling home prices to continue to eat into equity.

Source: Associated Press