The world population of 7.2 billion in mid-2013 is projected to increase by almost one billion people within the next twelve years, according to official United Nations population estimates (medium variant, 2012 Revision). It is projected to reach 8.1 billion in 2025, and to further increase to 9.6 billion in 2050 and 10.9 billion by 2100. This assumes a decline of fertility for countries where large families are still prevalent as well as a slight increase of fertility in several countries with fewer than two children per woman on average.
Small differences in the trajectory of fertility during the next decades will have major consequences for population size, structure, and distribution in the long run. The 'high-variant' projection depicted in the figure above, for example, which assumes an extra half of a child per woman (on average) compared to the medium variant, implies a world population of 10.9 billion in 2050 and 16.6 billion in 2100. The 'low-variant' projection, where women have half a child less, on average, than under the medium variant, would produce a population of 8.3 billion in 2050.
Almost all of the additional 3.7 billion people from now to 2100 will enlarge the population of developing countries, which is projected to rise from 5.9 billion in 2013 to 8.2 billion in 2050 and to 9.6 billion in 2100. Much of the overall increase between 2013 and 2050 is projected to take place in high-fertility countries, mainly in Africa, as well as countries with large populations such as India, Indonesia, Pakistan, the Philippines and the United States of America.
Growth is expected to be particularly dramatic in the least developed countries of the world, which are projected to double in size from 898 million inhabitants in 2013 to 1.8 billion in 2050 and to 2.9 billion in 2100. High population growth rates prevail in many developing countries, most of which are on the UN’s list of 49 least developed countries. Between 2013 and 2100, the populations of 35 countries could triple or more. Among them, the populations of Burundi, Malawi, Mali, Niger, Nigeria, Somalia, Uganda, United Republic of Tanzania and Zambia are projected to increase at least five-fold by 2100.
In contrast, the population of the more developed regions is expected to change minimally, passing from 1.25 billion in 2013 to 1.28 billion in 2100. The net increase is due largely to migration from developing to developed countries.
Populations of 43 countries or areas are expected to decrease between 2013 and 2050; of these, 40 are expected to continue to decrease between 2050 and 2100. Several countries are expected to see their populations decline by more than 15 per cent by 2050, including Belarus, Bulgaria, Croatia, Cuba, Georgia, Latvia, Lithuania, Republic of Moldova, Romania, the Russian Federation, Serbia, and Ukraine.
Currently the population of the less developed regions is still young, with children under age 15 accounting for 26 per cent of the population and young persons aged 15 to 24 accounting for a further 17 per cent. The numbers of children and young people in the less developed regions are at an all time high (1.7 billion children and 1.1 billion young people), posing a major challenge for their countries, which are faced with the necessity of providing education and employment to large cohorts of children and youth. The situation in the least developed countries is even more pressing, as children under age 15 constitute 40 per cent of their population and young people account for a further 20 per cent. In the more developed regions, children and youth account for 16 per cent and 12 per cent of the population, respectively.
In both the more and the less developed regions, the number of people in the main working ages, from 25 to 59 years, is at an all-time high: 608 million and 2.6 billion, respectively. Yet, whereas in the more developed regions that number is expected to peak in 2013 and decline thereafter, reaching 533 millions in 2050 and 504 million in 2100, in the less developed regions it will continue rising, reaching 3.7 billion in 2050 and 4.1 billion in 2100. In developing countries, this population is projected to increase by over 400 million within the next decade. These population trends point to the urgency of supporting employment creation in developing countries as part of any strategy to address the slow economic recovery that the world is experiencing.
Declining fertility and longer lives contribute to an older world. Globally, the number of persons aged 60 or over is expected to more than triple by 2100, increasing from 841 million in 2013 to 2 billion in 2050 and close to 3 billion in 2100. Already 66 per cent of the world’s older persons live in the less developed regions and by 2050, 79 per cent will do so. By 2100, this figure will reach 85 per cent.