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.