This paper examines the optimal direction of marginal income tax reform in the context of New Zealand, which recently reduced its top marginal income tax rate to one of the lowest in the OECD. A behavioural microsimulation model is used, in which social welfare functions are defined in terms of...

This paper presents two 'non-welfarist' approaches and one 'welfarist' approach to decompose changes in inequality and social welfare into three components. We distinguish the contributions of population, tax policy and labour supply behavioural effects. As an illustration, we decompose changes...