Originally published in 1976, the 14 papers in this collection discuss the history and significance of the concept of 'involuntary unemployment’, particularly as seen from a Keynesian perspective. The micro-economic foundations of employment and job-search theory and the measurement and the significance of employment statistics are also examined. Later sections consider aspects of unemployment as economic indicators and the relationship between unemployment and vacancies, as well as the social aspects of unemployment. A final chapter considers employment policies during the 20th century in the light of managing the economy.