Standard & Poor's said Wednesday that it is launching a national version of the widely-followed S&P/Case-Shiller Home Price Indices. The new S&P/Case-Shiller U.S. National Home Price Index will track the value of single-family homes across the United States, and will be calculated on a quarterly basis. The index will cover all nine U.S. Census divisions to estimate the aggregate value of single housing stock in the U.S., Standard & Poor's said. "For most Americans, their home is one of their most important assets. In a time like now when there are mounting questions about the future direction of the overall housing market and its impact on the economy, an accurate measure of national home values is particularly important," said David Blitzer, managing director at Standard & Poor's. "Therefore, Standard & Poor's is pleased to expand the coverage of our S&P/Case-Shiller Home Price Indices to include a comprehensive, national measure of the value of single family homes across the United States." "For the first time, market observers and global investors will have a readily-available national index that correctly follows the value of investments in housing through time, providing a true measure of value that captures all market segments -- regardless of financing type," said Robert Shiller, chief economist of MacroMarkets. "The wide universe of recent home sale transactions -- not merely the significantly diminished portion associated with conforming mortgages -- is reflected in this and other S&P/Case-Shiller(R) Home Price Indices. Now more than ever, the market cannot afford to ignore the significant impact that home values securing the collectively dominant subprime, jumbo, other non-conforming and portfolio mortgages have on real estate price trends and the economy at large." To be eligible for inclusion in the index, a house must be a single-family dwelling. Condominiums and co-ops are specifically excluded. Homes included in the index must also have two or more recorded arms-length sale transactions. As a result, no appraisal data are used, and new construction is excluded. Standard & Poor's will continue to publish its tradtional 10-city and recently-expanded 20-city composite indices on a monthly basis, along with individual metro area indices. For more information, visit http://www.standardandpoors.com.