An enormous and ever-expanding quantitative data base now exists for the study of modern economic growth. The World Bank currently makes available a data archive for over two hundred countries since 1960 embracing a wide variety of economic and social indicators (World Bank, 2001). Working explicitly in Kuznets’ tradition, Angus Maddison (1995) has pieced together from the ever-growing data base time series on national product going back one to two centuries for 56 developed and less developed nations. Robert Summers and Alan Heston (1991) following the lead of Kuznets’ student, Irving B. Kravis, have developed data since 1950 for 152 countries on national product and its components carefully adjusted for international differences in purchasing power. Economic historians have compiled a variety of time series statistics for countries in Europe, Asia, and Latin America (., Mitchell 1975). To a large extent this immense body of data represents the fulfillment of Kuznets’ vision of a quantitative framework for the systematic study of economic growth. For most scholars in the field today — economic historians and economic theorists alike — these data both define the object of study and provide the testing ground for theory. Thus has the study of economic growth been redirected much as Kuznets advocated — a vision become reality.