This book demonstrates how the reliable measurement of growth in tax revenues, both for a tax system and for its component taxes, is important for the design of tax policy. The need for discretionary changes in tax parameters (such as tax rates, income thresholds and allowances) is conditional on the expected automatic revenue growth generated by the tax system. The properties that generate these automatic revenue changes are referred to as the built-in flexibility, or revenue responsiveness, of the tax. This concept is the central focus of the analyses in this book, which provides an invaluable review and synthesis of analytical results and demonstrates how this concept can be applied in practice to yield estimates of revenue responsiveness in various countries. John Creedy and Norman Gemmell highlight how an understanding of the principal determinants of a tax system's responsiveness, and a knowledge of the relevant magnitudes, are important for the design and reform of tax policy where both revenue and redistributional considerations are typically central to the policy agenda.