Distributional effects are often central policy issues in debates over tax legislation. Although economic analysis can be used to estimate the distribution of the tax system, or a tax change, it cannot be used to provide a normative or prescriptive analysis. Descriptive analyses indicate the expected effects of policies, but normative analyses indicate the optimal policy. This book discusses different philosophies about how the tax burden should be distributed, and what those philosophies imply for the shape of the tax system. It addresses the question of the justifications for a progressive tax system, as well as the measures that can be used to characterise the distributional effects of tax changes.