The emerging market index is down 13 percent, with the Russell 2000 Index of small capitalization properties off 16 percent.

FORBES: Winning Hands In The Battle For Investment Survival

The only properties in the Dow Jones industrial index with depressed earnings are Boeing, Union Carbide, International Paper and Eastman Kodak.

FORBES: Dow 10,000 -- in 2005

The Registry's price index is calculated by measuring only the change in the price of properties that have been sold before, to ensure a proper comparison.

BBC: House price surveys explained

Real estate derivatives are a way for investors to gain exposure to the asset class without the need to buy or sell properties by replacing the exposure of the real property to the performance of a real estate return index.

FORBES: A Guide To Real Estate Derivatives