Personal Income Tax Structure: Theory and Policy

There is now a large and complex literature on optimal income taxation, within the context of second-best welfare economics. This paper considers the potential role of this analysis in the practical design of direct tax and transfer structures. It is stressed that few results are robust, even in simple models, in view of the important role played by alternative social welfare functions, the nature of the distribution of abilities and the preferences of individuals. In view of these negative results, it is suggested that a range of empirical tax analyses, capturing particular issues, can provide helpful guidance for policy analysts. Numerical illustrations are provided, paying attention to the role of a ‘top’ marginal tax rate applied to higher-income groups. In particular, behavioural microsimulation models can be used to examine marginal direct tax reform. Such models have the advantages of capturing the full extent of population heterogeneity and the complexity of the tax structure.