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How to Count Humans

A major new study based on a somewhat original methodology forecasts that global population will peak well before the end of this century. Although the usual caveats apply, the authors have offered fruitful new ways to grasp crucial policy questions.

NEW YORK – New research published this July in The Lancet forecasts that continued growth “through the century is no longer the most likely trajectory for the world’s population.” Rather, the global population is likely to peak in 2064 at 9.7 billion, before declining to 8.8 billion by 2100. The authors project that the populations of 23 countries – notably Japan, Thailand, Spain, and Ukraine – will be at most half their 2017 size by 2100, while the population of “another 34 countries will probably decline by 25-50%, including China, with a forecasted 48.0% decline.”

By contrast, Nigeria’s population is expected to grow 3.8-fold between 2017 and 2100, though its average fertility rate is expected to drop from 5.1 to 1.7 – that is, below replacement level and below that of Sweden (1.8 children per woman) in 2017. Nigeria was the only Sub-Saharan African country to rank among the world’s ten most populous countries in 2017. Yet by 2100, that list is expected to include the Democratic Republic of the Congo, Ethiopia, and Tanzania.

Of the four most populous countries today after China, India and Indonesia are expected to experience a population decrease, whereas the United States and Pakistan are expected to grow, albeit for different reasons. The increase in the US would be driven by immigration, making up for a decline in the fertility rate from 1.8 to 1.5. In Pakistan, the authors anticipate that population growth will be driven by the higher fertility rate, though they expect it to fall from 3.4 to 1.3 by 2100 – below the US’s current or projected rate.

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