Ebook: State and Local Population Projections: Methodology and Analysis

The initial plans for this book sprang from a late-afternoon conversation in a hotel bar. All three authors were attending the 1996 meeting of the Population As- ciation of America in New Orleans. While nursing drinks and expounding on a variety of topics, we began talking about our current research projects. It so happened that all three of us had been entertaining the notion of writing a book on state and local population projections. Recognizing the enormity of the project for a single author, we quickly decided to collaborate. Had we not decided to work together, it is unlikely that this book ever would have been written. The last comprehensive treatment of state and local population projections was Don Pittenger’s excellent work Projecting State and Local Populations (1976). Many changes affecting the production of population projections have occurred since that time. Technological changes have led to vast increases in computing power, new data sources, the development of GIS, and the creation of the Internet. The procedures for applying a number of projection methods have changed considerably, and several completely new methods have been developed.

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This book focuses on the methodology and analysis of state and local population projections. It describes the most commonly used data sources and application techniques within each of three classes of projection methods (cohort-component, trend extrapolation, and structural models) and covers the components of population growth, the formation of assumptions, the development of evaluation criteria, and the determinants of forecast accuracy. It considers the strengths and weaknesses of various projection methods, paying special attention to the unique problems of making projections for small areas, and closes with an examination of technological and methodological changes affecting the production of small-area population projections. The authors provide practical guidance to demographers, planners, and other analysts called on to construct state and local population projections. They use many examples and illustrations and present suggestions for dealing with special populations, unique circumstances, and inadequate or unreliable data; they also describe techniques for controlling one set of projections to another and for interpolating between two projections. They discuss the role of judgment and the importance of the political context in which projections are made. They emphasize the "utility" of projections, or their usefulness for decision making in a world of competing demands and limited resources. This comprehensive book will provide readers with an understanding not only of the mechanics of commonly used population projection methods, but also of the many complex issues affecting their construction, interpretation, evaluation, and use.