In this volume, economists discuss the long-run consequences of aging societies. Using theoretical economic models, long-term projections and simulations, and econometric analysis, answers to the following questions are given: What are the economic consequences for consumption patterns, the supply of labor, capital accumulation, productivity, and the international flow of capital? Where are the political consequences for pension systems, health care and immigration policy? And what changes in politics are needed to handle the issues of populations that age markedly?