Calculating Hedonic Price Indices with Unobserved Product Attributes : An Application to the UK Car Market

We show that hedonic price indices that omit model-specific unobservable product attributes are subject to considerable bias. We utilize a complete panel of new car versions marketed in the UK over 1971-98 which incorporates over 100 observable product characteristics, sales weighting to capture the distribution of purchases across models, and model-specific fixed effects to account for unobservable characteristics. We find that quality-adjusted prices obtained from hedonic regressions that do not account for unobservable characteristics exhibit a severe downward bias. We also show that quality-adjusted prices exhibit distinct sub-market differences having increased in mass production segments and decreased in 'specialized niches'