다국어인구학사전, 두 번째 통합본, 한국어판

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Population projections¹ are calculations which show the future development of a population when certain assumptions are made about the future course of population change, usually with respect to fertility, mortality and migration. They are in general purely formal calculations, developing the implications of the assumptions that are made. A population forecast² is a projection in which the assumptions are considered to yield a realistic picture of the probable future development of a population. Although the projection period³ is variable, short-term forecasts⁴ are the rule, as the margin of error to which forecasts are subject increases considerably as the length of the forecast’s period increases. The most frequently used method of projection is the component method⁵ or cohort-component method⁵ which takes the population distributed by age and sex at a base date⁶ and carries it forward in time, cohort by cohort, on the basis of separate allowances for fertility, mortality and migration. When matrix algebra is used for component projections, the method is sometimes called matrix method of projection⁷.

• 1. Projections are also made in terms of educational, economic and social characteristics. Backward projections which might be more accurately called retrojections, use similar methods to trace the past evolution of the population.

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Estimates of the population¹ by size and composition at various dates in the past and present may be made by various methods, including many of the methods used for population projections (720-1). Demographic estimates² include estimates of the population and of such characteristics as fertility (601-1), mortality (401-1), etc. Intercensal estimates³ relate to dates intermediate to two or more censuses (202-1), and take the results of these censuses into account. The error of closure⁴ is the difference between the size of a population enumerated at a new census and the population estimated for that census date on the basis of a previous census, the excess of births over deaths, and net migration (805-2) during the intercensal period. This difference represents the balance of errors in the data on births, deaths, net migration, and the coverage of the two censuses.

• 3. Postcensal estimates take the results of a previous census into account, but not those of the next census.