Thomas Büttner (2000)
Ageing of the World Population in the 21st Century*
In: Zeitschrift für Bevölkerungswissenschaft, Vol. 25, 3-4/2000, p. 441-458, Opladen: Verlag Leske + Budrich, ISSN: 0340-2398
The demographic transition towards low fertility and mortality "produces" wide-ranging effects on the age composition of the populations. Firstly, the typical course of the demographic transition brings about a juvenation of the populations: as mortality falls, in particular among the younger age groups, the number of surviving children increases. Hence, younger age groups are given greater emphasis, and populations tend to become younger. In the later phases of the demographic transition, both a fall in fertility and a drop in mortality have the converse effect of demographic ageing. The dynamics of the ageing processes are described by reference to three major age groups: Children (persons aged under 15), persons in working age (15 to under 60) and the elderly (60 years and older). The demographic data used have been taken from the 1998 revision of the "World Population Prospects" (United Nations 1999a, 1999b, 2000a) and the long-term projections based upon them (United Nations 2000b). The effect of the demographic transition is that demographic differences between the countries of the Earth – at least for a time – increase dramatically because the start and the duration of the transition from high to low fertility and mortality vary from country to country, and because countries are therefore at differing stages in this demographic transition at a given point in time. For this reason, the proportion of the elderly among the population is tending to become more differentiated.
* Original title: Die Alterung der Weltbevölkerung im 21. Jahrhundert (full text in German only)