UNITED NATIONS (AFP) - The world's population will hit 7.2 billion next month and is projected to reach 10.9 billion by 2100, powered by births in poor countries, the United Nations (UN) said on Thursday.
But, with the number of future global dwellers linked to fertility, the number at the end of the century could be as high 16.6 billion or even fall to 6.8 billion,, the UN said in its World Population Prospects.
Focusing on a conservative projection between these two, population growth is expected to be especially dramatic in the poorest parts of the world.
The population of developing countries is projected to rise from 5.9 billion in 2013 to 8.2 billion in 2050 and 9.6 billion 2100, the report said.
The poorest are projected to double in size from 898 million inhabitants of what the report defines as less developed countries this year to 1.8 billion in 2050 and to 2.9 billion in 2100.
In contrast, the population of the planet's more developed regions is not expected to change much, shifting upwards only slightly from 1.25 billion this year to 1.28 billion in 2100.
The report said the number of people in the richest countries would decline if it were not for an increased migration from poorer areas, projected to average about 2.4 million people a year from 2013 to 2050.
Much of the increase in world population between 2013 and 2050 - when the total is forecast to reach 9.6 billion - is projected to take place in countries with high fertility rates, mostly in Africa.
In fact, half of all population growth between 2013 and 2100 is expected to be concentrated in just eight countries: Nigeria, India, Tanzania, the Democratic Republic of Congo, Niger, Uganda, Ethiopia and the United States.
In more developed parts of the world, 23 per cent of the population is already 60 years or older, with that proportion projected to reach 32 per cent in 2050 and 34 per cent in 2100.
Globally, the number of people 60 years or older is expected to triple by 2100 to hover near 3 billion, with the proportion of older citizens in developing countries to more than double by 2050 and triple by the end of the century.