This magisterial volume follows four others covering Africa, Asia, Latin America and European transition economies. In 90 figures and 123 tables, it presents the results of detailed econometric work on the nature and extent of agricultural policy ‘distortions’ and their impacts on markets and welfare. Its main chapters survey these topics in nine groups of 77 ‘focus countries’, which account for nearly all of the world's agricultural production and farmers. Then, after analyses of additional distortion indicators at country and commodity level, a final chapter examines the economy-wide effects of policy reform over the three decades to 2004. It is estimated that agricultural policy reforms since the early 1980s have improved global economic welfare by US$233 billion per year, of which about two-thirds have accrued to high-income countries, although developing countries have gained more (1.0%, compared to 0.7%) as a proportion of national income. If trade liberalization for all goods were to be completed, further annual global welfare gains of US$168 billion would result, with similar but somewhat more emphasized effects. Most of these gains would come from agricultural policy reform, especially for developing countries and especially their unskilled workers. These results suggest that much poverty and inequality (and world market instability) could be alleviated by such further policy reform, as is being pursued in the ongoing World Trade Organization Doha Development Agenda.