Age structure as a factor of the future population dynamics

The paper estimates impact of the age structure of population on its future dynamics. In order to obtain such estimates we analyze the age structures and consider the results of calculating the forecast population dynamics at two forecast scenarios (1% increase in fertility and decrease in mortality and, vice versa, 1% decrease in fertility and increase in mortality) for 14 countries of the world (Belarus, Brazil, China, Germany, India, Iran, Japan, Nigeria, Poland, Russia, South Africa, South Korea, and the USA). We find significant cross-country variation in the difference of the relative population growth in 2015-2049 between these two forecast variants. This difference is the greatest in Nigeria and the smallest in Japan, Italy, South Korea, and Germany. We assume that the smaller this difference is, the greater is the impact of age structure upon population dynamics. Cross-country differentiation in the extent of this impact is due to differences in the population age structure. The results of the research (based on the multi-factor linear regression) show that the differences in the extent of such impact are stipulated by the configuration of the age structure and, first of all, by the share of population under 20. The impact of the degree of deformation of the age structure is much weaker (to estimate the degree of deformation we use the indicators characterizing the dissimilarity of the actual age structure from the age structure of the stable population, namely the standard deviation of the former from the latter, and the difference between the crude vital rates and the present rates of the natural increase of the population).