Abstract: The past 200 years have witnessed a revolution in global fertility, mortality, and population growth rates, in which the demography and health of human populations have been transformed. Vast gender and geographical inequalities in income and health persist, and new threats such as HIV/AIDS, environmental degradation, and population ageing have emerged. In July a special session of the United Nations General Assembly met to consider global progress in implementing the programme of action agreed at the 1994 international conference on population and development in Cairo.1 It approved far reaching recommendations for dealing with global trends in reproductive health and population.
Fig 1.
World population size (line) and annual increments (bars), 8000 BC to 2050 AD
This article reviews the transition in world health and population, and considers the changes that lie ahead. The economic and environmental implications of changes in the size, structure, and consumption patterns of world population are discussed in the other papers in this issue.
#### Summary points
More people were added to the world's population in the past 50 years than in the preceding million, and world population is expected to reach about 9 billion by 2050
Substantial growth in world population during the next century is inevitable because, although world fertility is lower than ever before, the high fertility of previous generations means that growing cohorts of future parents are already born
The largest increases in world population will occur in countries where poverty and unemployment are endemic, with Africa's share rising from 13% to 22% by 2050
All regions will experience population ageing: the number of people aged 60 and over will increase fourfold by 2050, their proportion rising from 9% of the total to 21%
Population policies will need to address the socioeconomic and environmental implications of changes in the size, structure, and consumption patterns of world …