S&P/Case-Shiller Home Price Index
The S&P/Case-Shiller Home Price Indices were designed as a benchmark of housing prices in the U.S. Their purpose is to measure the average change in home prices in a particular geographic market. 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 U.S. National Home Price Index (“the U.S. national index”) tracks the value of single-family housing within the United States. The index is a composite of single-family home price indices for the nine U.S. Census divisions and is calculated quarterly.
The indices measure changes in housing market prices given a constant level of quality. Changes in the types and sizes of houses or changes in the physical characteristics of houses are specifically excluded from the calculations to avoid incorrectly affecting the index value.
The monthly S&P/Case-Shiller Home Price Indices use the “repeat sales method” of index calculation. In other words, the methodology uses data on properties that have sold at least twice to capture the true appreciated value of each specific sales unit.
The quarterly S&P/Case-Shiller U.S. National Home Price Index aggregates nine quarterly U.S. Census division repeat sales indices using a base period and estimates of the aggregate value of single-family housing stock for those periods.
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).