United Nations population estimates and projections with special reference to the Arab world.

The United Nations Population Division has been preparing world population estimates and projections by region since 1951, by country since 1958, and by sex and age for each country since 1968. The latest revision of the projections was prepared in 1978. The 2 basic methods of preparing population projections are mathematical and component, and the component methods are most widely used at present, by both national governments and the United Nations. Before projections are prepared, the base data must be evaluated and adjusted. In the UN projections, the assumptions imply that orderly progress will be made and that there will be no catastrophes such as famines and epidemics during the projection period. The projectins are prepared in 4 variants--"medium", "high," "low," and "constant." A major source of uncertainty in populations arises from the problem of estimating future fertility. Changes in fertility affect the age distribution and the total population size more than changes in mortality. At the UN, mortality assumptions are initially made in terms of life expectancy at birth and then in terms of age-sex patterns of probabilities of survival corresponding to different life expectancy levels at birth. Some of the results of the 1978 revision of the medium variant of the estimates and projections are shown in table form. The world total population of 4,033,000,000 in 1975 is projected to reach 6,199,000,000 by the year 2000. Among the major areas and regions of the world, the most rapid population growth for the future is projected for the Arab countries, Africa and Latin America. Of the 2 Arab regions, North Africa and Southwest Asia, Southwest Asia is expected to have the higher rate of growth because of assumed continued immigration. Within the Arab regions, there has been an increasing diversity in the rate of population growth. This divergence is expected to narrow with assumed decreased migration rates during the 1980s.