What U.S. housing-market index was widely cited as evidence of the 2008 crash's home-price collapse?

The S&P/Case-Shiller Index was widely cited to measure the U.S. home-price collapse during the 2008 financial crisis.

The index tracks changes in residential property values using repeat sales of the same homes. Its methodology was developed by economists Karl Case and Robert Shiller, with Allan Weiss also involved in the commercial development of the index. Because it focuses on repeat transactions, it helps distinguish price changes from differences in the types of homes sold.

During the housing downturn, the national Case-Shiller index documented a historic fall in U.S. home prices. The collapse damaged household wealth and undermined mortgage-backed securities held by banks, insurers, and investors. Falling prices also left many homeowners owing more than their homes were worth.

The index is not a stock-market measure and should not be confused with the Dow or the S&P 500. It is a housing indicator whose data helped explain why mortgage losses spread into the broader financial system. Standard & Poor’s later became the index’s prominent brand partner.