The world’s population is getting older and growing at a slower pace but is still expected to increase from 7.7 billion now to 9.7 billion in 2050, the United Nations has said.

The UN Department of Economic and Social Affairs’ Population Division said in a report that world population could reach a peak of nearly 11 billion around the end of the century.

But Population Division director John Wilmoth cautioned that because 2100 is many decades away this outcome “is not certain, and in the end the peak could come earlier or later, at a lower or higher level of total population”.

The new projections indicate that nine countries will be responsible for more than half the projected growth between now and 2050: India, Nigeria, Pakistan, Congo, Ethiopia, Tanzania, Indonesia, Egypt and the US.

In sub-Saharan Africa, population is projected to nearly double by 2050, the report said.

Under-secretary general for economic and social affairs Lu Zhenmin said: “Many of the fastest growing populations are in the poorest countries, where population growth brings additional challenges in the effort to eradicate poverty,” promote gender equality and improve health care and education. 

The report confirmed the world’s population is growing older due to increasing life expectancy and falling fertility levels.

The global fertility rate fell from 3.2 births per woman in 1990 to 2.5 in 2019 and is projected to decline further to 2.2 by 2050.

A fertility rate of 2.1 births per woman is need to ensure population replacement and avoid declines, according to the report.

In 2019, the fertility rate in sub-Saharan Africa was the highest at 4.6 births per woman, with Pacific islands, northern Africa, and western, central and southern Asia above the replacement level, the report said.

But since 2010, it said 27 countries or areas have lost 1% or more of their population.

“Between 2019 and 2050 populations are projected to decrease by 1% or more in 55 countries or areas, of which 26 may see a reduction of at least 10%,” the UN said.

“In China, for example, the population is projected to decrease by 31.4 million, or around 2.2%, between 2019 and 2050.”

Mr Wilmoth said the growth rate is slowing as the fertility level gradually decreases. That decrease usually follows a reduction in the mortality level that initially instigated growth, he said.

He stressed that multiple factors lead to lower fertility including increasing education and employment, especially for women, and more jobs in urban than rural areas, which motivate people away from costly large families to smaller families.

To achieve this, he said, people also need access to modern contraception.

According to the World Population Prospects 2019 report, migration is also a major component of population growth or loss in some countries.

Between 2010 and 2020, it said 14 countries or areas will see a net inflow of more than a million migrants while 10 countries will experience a similar loss.

For example, some of the largest outflows of people — including from Bangladesh, Nepal and the Philippines — are driven by the demand for migrant workers, the report said. But some migrants are driven from their home countries by violence, insecurity and conflict, including from Burma, Syria and Venezuela.

The UN said countries experiencing a net inflow of migrants over the decade include Belarus, Estonia, Germany, Hungary, Italy, Japan, Russia, Serbia and Ukraine.