Population change and population forecasts are receiving considerable attention from governmental planners and policy-makers, as well as from the private sector. Old patterns of population redistribution, industrial location, labor-force participation, household formation, and fertility are changing. The resulting uncertainty has increased interest in forecasting because mere extrapolations of past trends are proving inadequate. In the United States of America popUlation forecasts received even more attention after federal agencies began distributing funds for capital infrastructure to state and local governments on the basis of projected future populations. If the national government had based those funding decisions on locally prepared projections, the optimism of local officials would have resulted in billions of dollars worth of excess capacity in sewage treatment plants alone. Cabinet-level inquiries concluded that the U. S. Department of Commerce should (1) assume the responsibility for developing a single set of projections for use whenever future population was a consideration in federal spending decisions and (2) develop methods which incorporate both economic and demographic factors causing population change. Neither the projections prepared by economists at the Bureau of Economic Analysis nor those prepared by demographers at the Bureau of the Census were considered satisfactory because neither method adequately recognized the intertwined nature of demographic and economic change. Against this background, the American Statistical Association (ASA) and the U. S.

Is rapid world population growth actually coming to an end? As population growth and its consequences have become front-page issues, projections of slowing growth from such institutions as the United Nations and the World Bank have been called into question. Beyond Six Billion asks what such projections really say, why they say it, whether they can be trusted, and whether they can be improved. The book includes analysis of how well past U.N. and World Bank projections have panned out, what errors have occurred, and why they have happened. Focusing on fertility as one key to accurate projections, the committee examines the transition from high, constant fertility to low fertility levels and discusses whether developing countries will eventually attain the very low levels of births now observed in the industrialized world. Other keys to accurate projections, predictions of lengthening life span and of the impact of international migration on specific countries, are also explored in detail. How good are our methods of population forecasting? How can we cope with the inevitable uncertainty? What population trends can we anticipate? Beyond Six Billion illuminates not only the forces that shape population growth but also the accuracy of the methods we use to quantify these forces and the uncertainty surrounding projections. The Committee on Population was established by the National Academy of Sciences (NAS) in 1983 to bring the knowledge and methods of the population sciences to bear on major issues of science and public policy. The committee's work includes both basic studies of fertility, health and mortality, and migration; and applied studies aimed at improving programs for the public health and welfare in the United States and in developing countries. The committee also fosters communication among researchers in different disciplines and countries and policy makers in government, international agencies, and private organizations. The work of the committee is made possible by funding from several government agencies and private foundations.

International migration is becoming an increasingly important element of contemporary demographic dynamics and yet, due to its high volatility, it remains the most unpredictable element of population change. In Europe, population forecasting is especially difficult because good-quality data on migration are lacking. There is a clear need for reliable methods of predicting migration since population forecasts are indispensable for rational decision making in many areas, including labour markets, social security or spatial planning and organisation. In addressing these issues, this book adopts a Bayesian statistical perspective, which allows for a formal incorporation of expert judgement, while describing uncertainty in a coherent and explicit manner. No prior knowledge of Bayesian statistics is assumed. The outcomes are discussed from the point of view of forecast users (decision makers), with the aim to show the relevance and usefulness of the presented methods in practical applications.