World population aging as a function of period demographic conditions

Abstract

BACKGROUND Population aging is a fundamental element of the demographic transition. In the absence of births, deaths, and migration, the mean age of any population will increase one year per calendar year. The intensity of period birth, death, and migration conditions (i.e., their crude rates and the difference between their mean age and the mean age of the population) either lessen or strengthen this natural tendency of populations to age. OBJECTIVE We investigate the contribution of births, deaths, and migration to population aging across the globe from 1950 to 2100. We examine whether a concerted pattern of population aging is associated with changes in period demographic conditions.