Planning transportation facilities for urban areas requires study, analysis, and forecasts of population, economic activity, and land use. These elements are the basic determinants of travel. This report deals with one of these elements, namely population forecasting. The report has been prepared to assist those having little or no background in demography to become acquainted with the general field and with the major population forecasting procedures in common use.
This report is not intended to serve as a textbook or an operational manual. Rather, it is a general introduction to the subject, a guide to more extensive works, and a source of information on data sources that have proven valuable in studying and forecasting population. The reader is cautioned that in reality the procedures are not as simple or clear cut as they may appear in this report. In actual practice, judgment plays a vital role in the preparation of any set of figures, and as much consideration must be given to the judgments used in a population analysis as to the method utilized.
Though population forecasting is treated in this report as an independent function, it must be recognized that population changes are to a great extent dependent on economic factors. Constant feed-back and comparison are essential here, as in most other phases of the planning process. The economic and population forecasts should be prepared so as to arrive at complementary results.
One of the first steps in any population study is to prepare a figure for the current population in the study area at the time of the forecast. In demographic terminology this is called "estimating," a term normally used to refer to calculations of current population. The terms "projection" or "forecast" normally refer to the anticipated population at some time in the future. Techniques for estimating current population are discussed in Appendix I.
A population forecast requires certain information on historic population counts, births, deaths, other rates which affect population change. Some of the most common sources of data are presented in Appendix II. This is not intended to be a complete listing of sources. Rather, the appendix provides the reader with a general idea of types of data available and where these data may be found.
As an aid to those who would like more information than is presented in this report, a bibliography has been compiled and is included as Appendix III. This bibliography, however,, is not a complete listing of the material available in the field. A more complete bibliography can be obtained in the publication by Hope T. Eldridge, The Materials of Demography , published by the International Union for the Scientific Study of Population and the Population Association of America in 1959.
Part I of this report is substantially the work of Van Beuren Stanbery, Better Population Forecasting for Areas and Communities." Part II also draws Heavily on Stanbery's report. This paper, currently out of print, was a guidebook prepared under the direction of the U. S. Department of Commerce in 1952. Mr. Stanbery's report has been revised to the extent necessary to bring the material up-to-date and to make the discussion more directly relevant to transportation planning studies. Thus, while the credit for the basic work goes to Mr. Stanbery, responsibility for any imperfections in the modifications is assumed by the Urban Planning Division (urban Development Branch) of the Bureau of Public Roads.