KENNETH J. ARROW is Joan Kennedy Professor of Economics Emeritus and Professor of Operations Research Emeritus at Stanford University. He has been President of the American Economic Association and the International Economic Association and has received the Nobel Memorial Prize in Economic Science. AMARTYA SEN is Lamont University Professor at Harvard University, and also Professor of Economics and Philosophy there. Previously he was the Drummond Professor of Political Economy at Oxford and, earlier, Professor of Economics at the London School of Economics, Delhi University and Jadavpur University. His publications include Collective Choice and Social Welfare; Choice; Welfare and Measurement; Poverty and Famines; On Ethics and Economics; and Inequality Reexamined, among others. He is past president of the Econometric Society, the International Economic Association, the Indian Economic Association and the American Economic Association. KOTARO SUZUMURA is Professor of Economic Systems Analysis at the Institute of Economic Research, Hitotsubashi University. He has taught at the London School of Economics, Stanford University, the Australian National University, the University of Pennsylvania, the University of British Columbia and, intermittently, at Kyoto University. He is a Fellow of the Econometric Society and Chief Editor of the Japanese Economic Review. He has published widely in professional journals including American Economic Review, Economica, Economic Theory, International Economic Review, the Journal of Economic Theory, the Journal of Public Economics and the Review of Economic Studies in the area of social choice, welfare economics and theoretical industrial organisation. He is also the author of Rational Choice, Collective Decisions and Social Welfare and Competition, Commitment and Welfare and is co-author of Economic Analysis of Industrial Policy.