A Varying Parameters Approach to Constructing House Price Indexes

Conventional housing price index models assume interperiod parameter stability and typically employ either repeat sales or hedonic methodologies. This paper introduces a method of index construction that combines multiple sales observations with single sale transactions while permitting characteristics prices from hedonic regressions to vary over time. A test for interperiod parameter stability is provided. Each period's data are arranged by location and repeat sales are matched by rows. This construction allows greater use of sample information and acknowledges the unique contribution of repeat sales to the estimation process. It also produces intertemporal error correlations that can be beneficially exploited by the seemingly unrelated regressions (SUR) technique. The paper also demonstrates a significance test for error correlation and discusses the treatment of unequal numbers of observations among index periods