They are calculated monthly and cover 20 major metropolitan areas (Metropolitan Statistical Areas or MSAs), which are also aggregated to form two composites – one comprising 10 of the metro areas, the other comprising all 20.
The S&P/Case-Shiller indices do not sample sale prices associated with new construction, condominiums, co-ops/apartments, multi-family dwellings, or other properties that cannot be identified as single-family.
The factors that determine the demand, supply, and value of housing are not the same across different property types. Consequently, the price dynamics of different property types within the same market often vary, especially during periods of increased market volatility. In addition, the relative sales volumes of different property types fluctuate, so indices that are segmented by property type will more accurately track housing values.
The S&P/Case-Shiller Home Price Indices originated in the 1980s by Case Shiller Weiss's research principals, Karl E. Case and Robert J. Shiller. At the time, Case and Shiller developed the repeat sales pricing technique. This methodology is recognized as the most reliable means to measure housing price movements and is used by other home price index publishers, including the Office of Federal Housing Enterprise Oversight (OFHEO).