Property Renovations and Their Impact on House Price Index Construction

This paper provides the first wide-scale analysis of property renovation bias in repeat-sales house price indices across a multitude of U.S. geographies. Property improvements frequently lead to positive quality drift. In local markets, omitting information on property improvements can bias index estimates upwards. Bias often varies in a predictable manner and can distort valuations by as much as 15 percent in the central districts of large cities. This systematic variation in bias is partially a function of the disparate concentration of renovation activity with property improvements occurring more frequently in denser areas. The distortionary effect of not accounting for property renovations tends to decline outside of downtown areas and is generally negligible in smaller cities (populations below 500,000)