A new study projects that global fertility rates, which have been declining in all countries since 1950, will continue to plummet through the end of the century, resulting in a profound demographic shift.
The fertility rate is the average number of children born to a woman in her lifetime. Globally, that number has gone from 4.84 in 1950 to 2.23 in 2021 and will continue to drop to 1.59 by 2100, according to the new analysis, which was based on the Global Burden of Diseases, Injuries, and Risk Factors Study 2021, a research effort led by the Institute for Health Metrics and Evaluation (IHME) at the University of Washington. The study was published Wednesday in the journal the Lancet.
“What we are experiencing now, and have been experiencing for decades, is something that we have not seen before in human history, which is a large-scale, cross-national, cross-cultural shift towards preferring and having smaller families,” said Dr. Jennifer D. Sciubba, a demographer and author of “8 Billion and Counting: How Sex, Death, and Migration Shape Our World,” who was not involved with the new research.
Dr. Christopher Murray, senior author of the study and director of IHME, said there are many reasons for this shift, including increased opportunities for women in education and employment and better access to contraception and reproductive health services.
Dr. Gitau Mburu, a scientist in the World Health Organization’s Department of Sexual and Reproductive Health and Research who wrote a comment that was published alongside the study, said in an email that economic factors such as the direct cost of raising children, the perceived risk of death to children and changing values on gender equality and self-fulfillment are all forces that may contribute to declining fertility rates. The relative contribution of these factors varies over time and by country, he added.
To maintain stable population numbers, countries need a total fertility rate of 2.1 children per woman, a number called the replacement level. When the fertility rate falls below the replacement level, populations begin to shrink.
The new analysis estimates that 46% of countries had a fertility rate below replacement level in 2021. That number will increase to 97% by 2100, meaning the population of almost all countries in the world will be declining by the end of the century.
A previous analysis by IHME published in the Lancet in 2020 predicted that the world population will peak in 2064 at around 9.7 billion and then decline to 8.8 billion by 2100. Another projection by the UN World Population Prospects 2022 predicted world population to peak at 10.4 billion in the 2080s.
Regardless of the exact timing of peak world population, it will likely begin declining in the second half of the century, Sciubba said, with dramatic geopolitical, economic and societal consequences.
