Horizontal and Vertical Equity in the New Zealand Tax-Transfer System: 1988-2013

Between 1988 and 2013 New Zealand’s tax and welfare systems have experienced a significant period of change, with real benefit payments and tax rates both declining. When evaluating the perceived fairness of these reforms the focus has predominantly fallen on how average economic activity and income inequality changed. However, such evaluation is partial at best. In this paper I intend to extend the evaluation of tax-transfer policy change during this period by reframing the adjustment in the distribution of income (as proxied by the Gini coefficient) due to policy into “horizontal equity”, “vertical equity”, and “reranking” effects. This decomposition is achieved by applying the observed tax-transfers systems to two sets of pooled years of HES data (1988-1991 and 2011-2013), and then constructing appropriate concentration coefficients to analyse how the tax system transformed pre-tax and transfer family income into disposable family income. Such a decomposition allows us to discuss how the observed changes could be consistent with a change in perceptions of what is fair (eg the importance of treating equals the same vs the importance of redistributing income)