This document examines trends in the United States population since World War II, and projects a scenario of how demographic and economic phenomena may evolve over the next several decades. The report is divided into five sections. Section 1 introduces the volume and discusses generally some of the effects of the nation's transition to zero population growth. The decline of birthrates will cause labor markets to tighten (wages will rise and unemployment will fall), but this will also encourage immigration to continue to increase. Section 2 attempts to explain why American fertility rates have changed, and argues that fertility rates will remain low, and perhaps decline. An economic model of fertility behavior is presented to explain fertility differences among couples, and the impact of the declining fertility rate on America's age structure is assessed. Section 3 discusses internal population redistribution, focusing on the increase of migrations out of major cities and to the south and west. The possible effects of these shifts on local governments is briefly considered. Section 4 analyzes the impact of rising immigration rates. Two factors are identified to explain the growth: the extreme imbalances in an increasingly international economy, and the political instability generated by the collapse of former spheres of influence. The general effects of immigration and appropriate government responses are described. Finally, Section 4 examines four areas in which massive policy changes are already underway in response to the population shifts: health care, military preparedness, Social Security, and education. (KH)