I have tried in this book to summarize where the world economy has come from in the past three centuries and to set out the core of the agenda that lies before us as we face the century ahead. This century, for the first time since the mid-18th century, will come to be dominated by stagnant or falling populations. The conclusions at which I have arrived can usefully be divided in two parts: one relates to what can be called the political economy of the 21st century; the other relates to the links between the problem of the United States playing steadily the role of critical margin on the world scene and moving at home toward a solution to the multiple facets of the urban problem. As for the political economy of the 21st century, the following points relate both to U.S. domestic policy and U.S. policy within the OECD, APEC, OAS, and other relevant international organizations. There is a good chance that the economic rise of China and Asia as well as Latin America, plus the convergence of economic stagnation and population increase in Africa, will raise for a time the relative prices of food and industrial materials, as well as lead to an increase in expen ditures in support of the environment. This should occur in the early part of the next century, If corrective action is taken in the private markets and the political process, these strains on the supply side should diminish with the passage of time, the advance of science and innovation, and the progressively reduced rate of population increase. The government, the universities, the private sector, and the professions might soon place on their common agenda the delicate balance of maintaining full employment with stagnant or falling populations. The existing literature, which largely stems from the 1930s, is quite illuminating but inadequate. And the experience with stagnant or falling population in the the world economy during post-Industrial Revolution times is extremely limited. This is a subject best approached in the United States on a bipartisan basis, abroad as an international problem. It is much too serious to be dealt with, as it is at present, as a domestic political football.