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Rapid Growth in Less Developed Regions
We are living in a world of unprecedented demographic change. After growing very slowly for most of human history, the world's population more than doubled in the last half century to reach 6 billion in late 1999. By 2006 it had reached 6.7 billion. Lower mortality, longer life expectancy and a youthful population in countries where fertility remains high all contributed to the rapid population growth of recent decades.
According to the 2008 Revision, the world population is expected to rise by 2.53 billion people, to reach a total of 9.1 billion in 2050. The increase alone is close to the total world population in 1950. Essentially all of the growth will take place in the less developed countries, and will be concentrated among the poorest populations in urban areas.
By contrast, the overall population of the more developed countries is likely to show little change over the next 41 years, remaining at about 1.2 billion. Fertility is below replacement level (2.1 children per woman) in all 45 developed countries or areas, as well as in 28 developing countries including China. The population of developed regions is ageing and would actually decline were it not for migration. The populations of Germany, Italy, Japan and most of the successor states of the former Soviet Union are expected to be lower in 2050 than they are today.
Projections dependent on continued declines in fertility
Fertility in the less developed countries as a whole is projected to decline from 2.75 children per woman in 2005-2010 to 2.05 in 2045-2050. The decline in the group of the 50 least developed countries is expected to be even sharper: from 4.63 children to 2.50 children per woman. However, realization of these projections is contingent on continued declines in fertility, even as funding for family planning has been declining.
Clearly, most people want and are having smaller families than in the past. This trend has been greatly helped by the wider availability of high quality, safe and affordable family planning services. Still, many people are having more children than they want to. Some 200 million women who would like to use contraceptives lack access to them.
Achieving the predicted projections will require expanded access to family planning, especially in the poorest countries. The urgency of this is clear: If fertility were to remain at current levels, the population would increase to 11 billion, with less developed nations' populations rising to 9.8 billion instead of the 7.9 billion that is projected. Even if fertility rates are lower than projected, the large proportion of young people still makes population growth until 2050 virtually inevitable.
Projected growth linked to sustained progress in HIV/AIDS prevention and treatment
The projected population trends also depend on achieving a major increase in the proportion of
AIDS patients who get anti-retroviral therapy to treat the disease and on the success of efforts to
control the further spread of HIV. In the 2008 Revision, the impact of the epidemic was modeled in 58 countries where adult HIV prevalence reached 1 per cent or higher at some point during 1980-2007 or where the number ofpeople living with HIV/AIDS was at least half a million in 2007. Among those 58 countries, 38 are in Africa and 15 had an adult HIV prevalence of at least 5 per cent in 2007.