World Population Prospects, the 2010 Revision

Figure 1: Estimated and projected world population according to different variants, 1950-2100 (billions)

Source: United Nations, Department of Economic and Social Affairs, Population Division (2011): World Population Prospects: The 2010 Revision. New York

(Updated: 15 April 2011)

Key result: The world population is expected to keep on rising during the 21^st century, although its growth is projected to experience a marked deceleration during the second half of the century.

According to the medium variant of the 2010 Revision of World Population Prospects, the world population is expected to increase from 6.9 billion in mid-2011 to 9.3 billion in 2050 and to reach 10.1 billion by 2100. Realization of this projection is contingent on the continued decline of fertility in countries that still have fertility above replacement level (that is, countries where women have, on average, more than one daughter) and an increase of fertility in the countries that have below-replacement fertility. In addition, mortality would have to decline in all countries.

If fertility were to remain constant in each country at the level it had in 2005-2010, the world population could reach nearly 27 billion by 2100. A future fertility that remains just half a child above that projected in the medium variant would result in a population of 15.8 billion in 2100 (high variant), but if fertility remains just half a child below that of the medium variant, the world population in 2100 could be 6.2 billion, the same size it had at the start of the 21^st century.

Today, 42 per cent of the world population lives in low-fertility countries, that is, countries where women are not having enough children to ensure that, on average, each woman is replaced by a daughter who survives to the age of procreation (i.e., their fertility is below replacement level). Another 40 per cent lives in intermediate-fertility countries where each woman is having, on average, between 1 and 1.5 daughters, and the remaining 18 per cent lives in high-fertility countries where the average woman has more than 1.5 daughter

Even if the fertility of each country would reach replacement level in 2010-2015, the world population would continue to increase over the rest of the century, reaching 9.1 billion in 2050 and 9.9 billion in 2100 (see the “instant replacement variant” in the figure above).