The essays center on a few broad themes: population and its relation to economic growth, capital formation in long historical perspective, the broader features of modern economic growth, and recent changes in the gap between the rich and poor countries. The themes are clearly interrelated. Even a selection on the supply of and demand for economic data bears on the others, since it deals with the conditions that limit the quantitative study of economic growth. Included in the volume and published for the first time in book form is Professor Kuznet's Nobel Laureate address, "Modern Economic Growth: Findings and Reflections."