GUILLERMO PERRY is Chief Economist for the Latin America and Caribbean region of the World Bank. He has been Minister of Finance and Public Credit, Minister of Mining and Energy, and director of two leading economic think-tanks in Colombia: FEDESARROLLO and CEDE. He has published a number of books on structural reform and economic policy. - JOHN WHALLEY has worked extensively in the tax and other policy areas, and is known for work on developing countries. A Research Associate of the National Bureau of Economic Research, he holds positions at the University of Western Ontario, Canada, and the University of Warwick, England. He is also a Fellow of the Econometric Society. - GARY MCMAHON is a Consultant at the World Bank, Washington.