During the past thirty-five years opinions on unemployment have significantly influenced our thoughts about the process of economic development in low-income countries, the economic strategies appropriate for governments committed to accelerating that process, and the best way for the rich nations to assist in that endeavour. Which of the many and sometimes conflicting opinions of economists regarding the magnitude, causes and costs of unemployment in LDCs reigns as the conventional wisdom at any given time is not determined by purely scientific criteria. The emergence of a particular set of hypotheses as dominant may be strongly influenced by the attitudes and political preoccupations of observers as well.