The next few decades will see a dramatic drop in the number of children being born in most parts of the world, sparking a “staggering social change” to the planet. 

The slump in fertility rates will be so profound that over three-quarters of countries will not be able to sustain their population size by 2050. In other words, their population will decline. By the end of the century, more than 97 percent of countries and territories will run into this problem. 

This is the chief finding of a new study on global fertility rates – the average number of children that are born to a woman over her lifetime – by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington’s School of Medicine.

However, we will likely have a “demographically divided world” on our hands. While fertility rates are forecasted to plummet in most parts of the world, there will be a surge of relatively high fertility rates in numerous low-income countries, predominantly in western and eastern sub-Saharan Africa. 

Around 77 percent of births are expected to occur in low- and lower-middle-income countries by the end of the century. For instance, 29 percent of the world’s babies were born in sub-Saharan Africa in 2021, but that’s projected to rise to over 54 percent of babies by 2100.

“We are facing staggering social change through the 21st century. The world will be simultaneously tackling a 'baby boom' in some countries and a 'baby bust' in others,” Professor Stein Emil Vollset, senior author from IHME, said in a statement sent to IFLScience.

 "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 aging 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."

In light of their findings, the researchers argue that we need to start planning for this future now. They believe that declining fertility rates will result in 76 percent of countries having a reduction in population size unless it’s offset by immigration or policies that offer greater support for parents – although managing the problem will not be simple. 

“There’s no silver bullet,” explained co-lead author Dr Natalia V. Bhattacharjee, lead research scientist from IHME. 

“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 aging societies are losing — a youthful population,” she added. 

The changes in fertility rates are primarily driven by two forces: access to modern contraceptives and female education. When facing the challenges ahead, the researchers believe we should not lose sight of the progress the world has made in terms of female empowerment. 

“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," continued Bhattacharjee. "It is well established that nations with strong women's rights are more likely to have better health outcomes and faster economic growth. It is imperative women’s rights are promoted and protected and that women are supported in having the number of children they wish and pursuing their careers.”

The study is published in the journal The Lancet.