Optimal taxation, the compensation principle and the measurement of changes in economic welfare

Abstract

This paper explores the implications of optimal taxation for the measurement of changes in economic welfare. It shows that the measure implied by the compensation principle — the sum of the relevant compensating variations — is only accurate in the presence of optimal lump-sum taxation: an unsurprising conclusion, but a gloomy one given that such taxation is generally infeasible. However, all is not lost. The paper uses the linear income tax case to show that it is possible to derive weights that can be attached to the relevant compensating variations to provide accurate measures of changes in welfare in the presence of second-best taxation: weights that can be calculated from observable data.