Understanding Changes in Progressivity and Redistributive Effects: The Role of Tax-Transfer Policies and Labour Supply Decisions

In this paper we propose a framework to study changes in the redistributive consequences of income taxes and transfers. In contrast with previous approaches the new method allows decomposition of the change in the redistributive impact into four components: the immediate effect of changes in the tax-transfer system in the absence of labour supply responses; the effect of labour supply changes induced by changes in the tax-transfer system; the effect of all other labour supply changes; and a residual capturing the variation not explained by the previous factors. We illustrate the use of our decomposition method by analysing the changes in the redistributive impact of the tax and transfer system in Australia between 1999 and 2007. We find that labour supply changes, and in particular the increase in employment rates over the period, explain to a large extent the observed reduction in the redistributive effect of the tax-transfer system. A sizable part of these labour supply changes were found to be direct responses to tax-transfer reforms. Interestingly, we find that tax reforms were not responsible for the observed reduction in tax progressivity.