![]() ![]() ![]() But that would require a significant rebound in many nations-in 2020, the fertility rate was about 1.4 in Finland-which Christopher Murray, the director of the IHME, told me there’s little evidence to support. The UNPD and CEPAM models both expect fertility to eventually reach a global average of about 1.75. ![]() In many of these countries, fertility has already fallen below replacement level-the rate needed for a population to replace itself from one generation to the next without immigration, which is about 2.1 children per woman. Instead, the rapid expansion of women’s access to modern education and effective contraception may accelerate the fertility decline.Īnother source of contention is what will happen to fertility in wealthy nations such as the United States, Finland, and Japan. But demographers at both CEPAM and IHME suspect that population shifts in 21st-century Africa won’t resemble those of, say, late-20th-century Asia or Latin America. ![]() In other words, fertility should fall in places such as sub-Saharan Africa at about the same rate it’s fallen elsewhere. The UNPD model posits that the best way to predict the future is to study the past, Wilmoth said. Although most demographers expect that women there will continue to have fewer children as the region develops economically, they don’t agree on how steep the decline will be. For example, the fertility rate is currently very high in sub-Saharan Africa, though it is declining. Only in the second half of the century do they begin to diverge.Ī number of assumptions underlie these discrepancies. That’s why, through about 2050, all three global-population forecasts mostly agree. You don’t need a fancy statistical model to know how many women of childbearing age are alive, or how old a baby born in 2021 will be in 30 years. In the short term, demographic forecasts are quite reliable, John Wilmoth, the UNPD’s director, told me. Scientists all seem to have different ideas about what to do next. The IHME’s-and, to a lesser extent, CEPAM’s-envisions extreme population aging, where, without considerable immigration, some countries could end up with an “inverted age pyramid” in which the old outnumber the young and the needs of elderly dependents strain the workforce supporting them. The UNPD’s points to a much more crowded planet, which some fear threatens to deplete natural resources and increase carbon emissions. If, as the saying goes, “demography is destiny” and population trends determine the prosperity of nations and the world, then these forecasts imply conflicting prophecies of our future challenges. (Though IHME’s stats are widely reported in the media, in August of last year, The Lancet published a letter signed by more than 150 experts calling for greater scrutiny of IHME’s forecast.) According to IHME, the global population will peak earlier still, at 9.7 billion in 2064, and then plummet by nearly 1 billion before the century is out. CEPAM projects that the population will peak at 9.8 billion around 2070–80 and then drop to about 9.5 billion by the end of the century. The UNPD’s most recent forecast predicts that the global population will reach about 10.9 billion by 2100 and could stabilize or even decline slowly thereafter. But over the past several years, two other prominent forecasts- one from the Centre of Expertise on Population and Migration (CEPAM) and another from researchers at the Institute for Health Metrics and Evaluation (IHME), at the University of Washington-have offered alternative narratives about humanity’s future. The UNPD has traditionally had sparse competition. They also assist environmental scientists in forecasting climate change. These forecasts help national leaders anticipate demand for food, water, and energy, as well as plan infrastructure projects and support systems for children and the elderly. In 1946, he was appointed director of the newly formed United Nations Population Division (UNPD), which continues to make global-population projections today. Nevertheless, Notestein’s work was foundational. The global population topped 6 billion by the millennium’s end, and has grown by nearly 2 billion more since. Frank Notestein, the founding director of the Office of Population Research at Princeton, estimated that about 3.3 billion humans would be on the planet by the year 2000. The number of people on Earth had more than doubled in the previous century and a half, to more than 2 billion, and experts worried that food production would not be able to keep pace. The first modern, comprehensive attempt to predict the human population’s long-term trajectory took place in 1945. ![]()
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