Decades of fretting about over-population and encouraging contraception and abortion have succeeded. But the dream of zero population growth has become a nightmare, a new study published in The Lancet suggests. Instead of stabilizing, population numbers keep falling.

Although by 2100 more than 97% of countries and territories will have sub-replacement fertility rates, comparatively high rates in low-income countries, predominantly in western and eastern sub-Saharan Africa, will continue to drive population increases in these locations throughout the century. This “demographically divided world” will have enormous consequences for economies and societies. 

The Lancet has published estimates from the Global Burden of Disease, Injuries, and Risk Factors Study (GBD) 2021 – a global research effort led by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington’s School of Medicine.

Countries need to have a total fertility rate (TFR) of 2.1 children per woman to maintain their population. The researchers estimate that by 2050, 155 of 204 (76%) countries and territories will be below replacement. The number of countries and territories below replacement will increase to 198 of 204 (97%) by 2100. Only immigration – which is always a highly contentious issue — will keep them from shrinking.  

These new fertility forecasts underscore the enormous challenges to economic growth in many middle- and high-income countries with a dwindling workforce and the growing burden on health and social security systems of an ageing population. 

In 2021, 29% of the world’s babies were born in sub-Saharan Africa; by 2100, this is projected to rise to over half (54%) of all babies. 

“We are facing staggering social change through the 21st century,” said the lead author Professor Stein Emil Vollset, from IHME. “The world will be simultaneously tackling a ‘baby boom’ in some countries and a ‘baby bust’ in others. As most of the world contends with the serious challenges to the economic growth of a shrinking workforce and how to care for and pay for ageing populations, many of the most resource-limited countries in sub-Saharan Africa will be grappling with how to support the youngest, fastest-growing population on the planet in some of the most politically and economically unstable, heat-stressed, and health system-strained places on earth.” 

“The implications are immense,” said co-lead author Dr Natalia V. Bhattacharjee. “These future trends in fertility rates and live births will completely reconfigure the global economy and the international balance of power and will necessitate reorganizing societies. Global recognition of the challenges around migration and global aid networks are going to be all the more critical when there is fierce competition for migrants to sustain economic growth and as sub-Saharan Africa’s baby boom continues apace.”  

Only six countries above replacement level in 2100 

The global TFR has more than halved over the past 70 years, from around five children for each female in 1950 to 2.2 children in 2021—with over half of all countries and territories below the population replacement level of 2.1 births per female as of 2021. This trend is particularly worrying for places such as South Korea and Serbia where the rate is less than 1.1 child for each female. 

But for many countries in sub-Saharan Africa, fertility rates remain high—the TFR of the region is nearly twice the global average, at four children per female in 2021. In Chad, the TFR of seven births is the highest in the world.

Over the coming decades, global fertility is predicted to decline even further, reaching a TFR of around 1.8 in 2050, and 1.6 in 2100—well below the replacement level. By 2100, only six of 204 countries and territories (Samoa, Somalia, Tonga, Niger, Chad, and Tajikistan) are expected to have fertility rates exceeding 2.1 births per female. In 13 countries, including Bhutan, Bangladesh, Nepal, and Saudi Arabia, rates are even predicted to fall below one child per female. 

The TFR in Western Europe is predicted to be 1.44 in 2050, dropping to 1.37 in 2100, with Israel, Iceland, Denmark, France, and Germany expected to have the highest fertility rates at between 2.09 and 1.40 at the end of the century. Rates are projected to be much lower across the rest of Europe and parts of Asia.   

Most of the world is transitioning into natural population decline (when the number of deaths exceeds the number of live births); just 26 countries are still projected to be growing in population in 2100, including Angola, Zambia, and Uganda. 

Pro-natal policies 

The study also examined the impact of pro-natal policies designed to provide financial support and care for children and families. The experience of countries that have implemented such policies suggests that these will only prevent countries from dropping to extremely low fertility levels (with just 30 countries and territories below a TFR of 1.3 in 2100 if pro-natal policies are implemented compared to 94 under the most likely scenario). 

“There’s no silver bullet,” said Bhattacharjee. “Social policies to improve birth rates such as enhanced parental leave, free childcare, financial incentives, and extra employment rights, may provide a small boost to fertility rates, but most countries will remain below replacement levels. And once nearly every country’s population is shrinking, reliance on open immigration will become necessary to sustain economic growth. Sub-Saharan African countries have a vital resource that ageing societies are losing—a youthful population.” 

 “There is very real concern that, in the face of declining populations and no clear solutions, some countries might justify more draconian measures that limit reproductive rights,” she warned.