World Population to Peak by 2064, Then Drop Nearly 1B by 2100

The world's population is expected to swell to 9.7 billion by 2064, before dropping to 8.8 billion in 2100, according to a new study.

The study, conducted by researchers at the University of Washington's Institute for Health Metrics and Evaluation (IHME) and funded by the Bill and Melinda Gates Foundation, was published by the journal The Lancet on Tuesday.

The population increase forecasted by the study, based on modelling using the Global Burden of Disease Study 2017, is significantly smaller than some other predictions. The United Nations expects a global population of 11.2 billion by 2100.

Although world population is expected to continue to rise from the current estimate of 7.8 billion for decades, the study found that a marked decline was likely to take place during the later half of the century. The population shift could force world leaders to rethink policies on key issues like immigration, according to the researchers.

"Continued global population growth through the century is no longer the most likely trajectory for the world's population," said IHME Director Dr. Christopher Murray, who led the research, in a statement.

"This study provides governments of all countries an opportunity to start rethinking their policies on migration, workforces and economic development to address the challenges presented by demographic change," Murray added.

The drop in population is expected due to fertility rates falling below levels needed to maintain population size. Rates are dropping quickly in sub-Saharan Africa and in countries including India and China. Researchers believe the fertility rates are likely to keep falling due to "continued trends in female educational attainment and access to contraception."

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Global population is expected to continue to increase and reach a peak of 9.7 billion in 2064, before declining to around 8.8 billion by 2100, according to researchers from the University of Washington. Hydromet/Getty

Regions of the world where the population is expected to decline most dramatically include Asia and Central Europe. China is predicted to have a population of 732 million by 2100, compared to 1.4 billion in 2017. Population is also expected to roughly halve in countries including Japan, Spain, Italy, Portugal and South Korea.

Despite sub-Saharan Africa's declining fertility rate, population in the area is expected to triple from 2017 levels to more than 3 billion by 2100, due to falling death rates and an increasing number of women reaching reproductive age. In North Africa and the Middle East, predicted population is 978 million in 2100, up from 600 million in 2017.

Population in the United States is expected to peak at 364 million in 2062, before dropping to 336 million 2100, around 8 million more than the country's current estimated population. Fertility rates in the U.S. are expected to steadily decline, but the population reduction is likely to be modest due to continued immigration.

The study predicts China will overtake the U.S. as the world's largest economy in 2035. However, the U.S. is expected to regain its status as world economic leader in 2098 due to immigration. Without continuing immigration, the country's workforce and economic growth are likely the stall, according to the researchers.

"This important research charts a future we need to be planning for urgently," said Dr. Richard Horton, The Lancet's Editor-in-Chief. "It offers a vision for radical shifts in geopolitical power, challenges myths about immigration, and underlines the importance of protecting and strengthening the sexual and reproductive rights of women. The 21st century will see a revolution in the story of our human civilisation."

"Africa and the Arab World will shape our future, while Europe and Asia will recede in their influence. By the end of the century, the world will be multipolar, with India, Nigeria, China, and the US the dominant powers," Horton added. "This will truly be a new world, one we should be preparing for today."