Measuring CPI's reliability: the stochastic approach to index numbers revisited

The reliability measurement of the Consumer Price Index (CPI) has recently drawn much attention, as the index number has been criticized for its inaccuracy in accessing the degree of inflation. This article centers on providing a new regression specification that can help better gauge the CPI's reliability. More specifically, based on the stochastic approach to index numbers, we argue that the conventional treatment of the systematic changes in relative prices should be made time variant. We therefore propose a more comprehensive regression specification by including additional dummies that represent different general inflation rate levels and business cycle phases. Under this framework, we are more capable of avoiding possible misspecifications in the regression equation, as was experienced by Clements and Izan (1987). It also allows us to better answer the ‘Keynes’ critic’ regarding the stochastic approach to index numbers. The empirical results of Australia and the US are used to validate the merit of our specification.