Now in its fourteenth annual edition, the World Development Report 1991 is an essential reference on the world economy and the state of social and economic development. This year's report is entitled 'The Challenge of Development Society', and it gives an in-depth, historical look at economic development since the end of World War II. It asks why economic development has varied so widely and how its pace and quality can be enhanced. Economic development is a sustained improvement in welfare - in per capita income and in such areas of social development as education, nutrition, life expectancy, and health. Culture, religion, values, natural resources, and the socio-political and historical contexts all play a part. WDR 1991 assesses the experience of developing as well as industrial countries to delineate the major factors that contribute to development. The analysis will focus on various country groupings and individual case studies. It will also consider the long-term environmental consequences of alternative development strategies.