In 2100, over 20 countries (including Japan, Spain, Italy, Thailand, Portugal, South Korea and Poland) will see their population decrease by at least half.
There were hints of abrupt changes in the world population in recent studies, but the trend indicated a slowdown. According to an important study published today, in 2100 the Earth will house 8,8 billion souls. Two billion less than the current United Nations projections. The cause? Mainly the drop in fertility.
By the end of the century, 183 of the world's 195 countries will have fallen below the replacement threshold needed to maintain population levels, according to an international team of researchers on The Lancet.
The main collapse, unbelievable if read today, will be for China. The celestial empire will see its population drop by 670 million in 80 years. That's equivalent to losing over 8 million people a year.
Sub-Saharan Africa, meanwhile, will triple in size to nearly three billion people, with Nigeria alone expanding to nearly 800 million by 2100, second only to India's 1,1 billion.
Good news? Sure?
"These predictions suggest good news for the environment," the report reads. "Less stress on food production systems and fewer carbon emissions, as well as significant economic opportunities for parts of sub-Saharan Africa."
The main author of the study is Christopher Murray, director of the Institute for Health Metrics and Evaluation (IHME) at the University of Washington.
"However," he adds, "most countries outside Africa will see the reduction of the workforce and the reversal of the population pyramids, with profound negative consequences for the economy." Ecco.
Founded in 2007 and supported by the Bill e & Melinda Gates Foundation, IHME has become a global reference for health statistics, especially its annual reports on the global effects of disease.
What to do?
For high-income countries, the best solutions to support population levels and economic growth will be flexible immigration policies and social support for families who want children, the study concludes.
Almost one billion people over eighty
Changes in world demographics will bring the absolute need to overhaul social services and health systems to manage much older populations.
Fertility decreases and life expectancy increases worldwide. As a result, the number of children under five is expected to decrease more than 40%.
At the other end of the spectrum, 2,37 billion people (more than a quarter of the world's population) will be over 65. Those over 80 will rise from about 140 million to 866 million.
Who will work?
The sharp decline in the number and proportions of the working-age population will pose enormous challenges in many countries. "Companies will struggle to grow with fewer workers and taxpayers," he noted Stein Emil Vollset, professor at IHME.
The number of people of working age in China, for example, will plummet from around 950 million today to just over 350 million by the end of the century. A 62% drop. In India, the decline will be less steep, from 762 to 578 million.
In Nigeria, by contrast, the active workforce will expand from 86 million today to over 450 million in 2100.
It is an earthquake. These changes will also end up shuffling the world's power relations.
A new multipolar world
By 2050 Chinese GDP will exceed that of the USA, but due to the changes subject to these forecasts, it should return to second place by 2100. Indian GDP will rise to third place while Japan, Germany, France and the United Kingdom will remain among the 10 major economies in the world.
Brazil will drop in the ranking by inhabitants from 8th place today to 13th place, Russia from 10th to 14th place. Italy and Spain will drop to 25th and 28th place respectively.
Indonesia could become the 12th global economy, while Nigeria (now 28th) would enter the top 10.
In short, by the end of the century, the world will be multipolar. India, Nigeria, China and the USA will be the dominant powers in a planet that will see radical changes in geopolitical power.
How did these predictions come about?
Small premise. Until now, the UN (which predicts 8,5, 9,7 and 10,9 billion people in 2030, 2050 and 2100 respectively) has practically had a monopoly on global population projections.
The difference between the UN figures and those coming out of the IHME essentially depends on the data on fertility rates. The so-called "replacement rate" for a stable population should be 2,1 children per woman.
UN calculations assume that countries with low fertility today will see such rates rise, on average, to about 1,8 children per woman.
"Our analysis," Murray says, "suggests that as women become more educated and have more access to health services, they choose to have fewer than 1,5 children on average."