This textbook is designed specifically for students of economics and the social sciences who are taking a first course in economic development and have a background knowledge of macro-and micro-economics. It draws on several branches of economics in order to elucidate and promote understanding of the development difficulties facing economies of the world's poor countries. This fifth edition, like its predecessor, combines descrption and analysis with an emphasis on the elaboration of simple and useful theoretical economic models for an understanding of the issues that comprise the subject-matter of development economics. All statistics have been updated and many of the chapters have been rewritten to accommodate new institutional changes and innovations in thinking about development strategy. A completely new chapter on the incorporation of environmental issues into social cost-benefit analysis, and the concept of sustainable development has been included.