These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: If present trends continue.
    Author: Haub C.
    Journal: Popul Today; 1986 Jan; 14(1):8-9. PubMed ID: 12267720.
    Abstract:
    Population projections are one of demography's more popular products, but they come with many implicit caveats. It is the Weather Bureau, not the Census Bureau, that makes forecasts. Weatherpeople do have a rather detailed "model" to go on that basically stays the same -- the earth and its atmosphere. Their model is filled with precedents to guide them. Demographers, by contrast, often have to make do with scanty or missing data, poor quality data, unpredictable behavior patterns, and many other obstacles. They consequently are quick to point out that their projections are based on assumptions for the future applied to current data, and even those "current data" may themselves contain assumptions. Projections themselves are never "wrong." Anyone can make perfect projections. The process of projecting a population is actually a fairly simple series of rote mathematical calculations, applying the components of change, fertility, mortality, and migration, to each age cohort. Yet, what good is a perfect projection, if the assumptions behind the projection turn out to be incorrect. Generally, it is best for demographers to use words like "expect" sparingly. When dealing with the population of large areas, such as Africa, it would seem that a medium projection would be a relatively safe number to quote, since it could be anticipated that the projections for individual African countries would be either too high and/or too low. It would be reasonable to expect a fair number of compensating errors. Yet, if concern is with a single country, then it would be best to expand the vision beyond medium projections. Future country populations can easily vary by factors of 3 and 4, while that of the entire region follows the medium projections rather well. Then, 1 Golden Rule of projections could be set down: the smaller the geographic area, the more one needs to inquire "how the trick was done." Everyone across the demographic spectrum concedes that someday population growth on earth must cease, simply because the total numbers eventually become so large. Because of that premise, for the sake of projecting future "stationary" population, the tendency is to assume that the 2-child family will be reached and forever maintained. Recently, very low birthrates have been reported in Europe, and some demographers are discussing whether the future holds longterm population decline, rather than the stationary population of replacement level fertility. The entire subject remains cloudy. Mortality assumptions usually play a much less important role than fertility. 1 reason to run projections is that the results of seemingly small shifts in assumptions can produce surprisingly different future populations. Projections are needed and desired, but in many ways are not "user friendly."
    [Abstract] [Full Text] [Related] [New Search]