Jul 18, 2020 - Health

Human population projected to shrink at end of century

The global population

Global population projections to 2100. Credit: The Lancet. Fertility, mortality, migration, and population scenarios for 195 countries and territories from 2017 to 2100: a forecasting analysis for the Global Burden of Disease Study

New projections suggest the human population will be smaller and significantly older by the end of the century.

Why it matters: As fertility rates continue to drop around the world, economic and political power among nations will shift rapidly, creating an international landscape radically different than it is in 2020.

Driving the news: A new report in the Lancet by researchers at the Institute for Health Metrics and Evaluation at the University of Washington forecasts the global population will peak in 2064 at around 9.7 billion before declining to 8.8 billion by the end of the century.

  • That slowed growth in the decades ahead followed by outright decline is chiefly caused by drastically falling total fertility rates, from 2.37 women per child globally today to 1.66 in 2100.
  • The fertility rate required to keep population stable is 2.1.
  • Not only will humanity shrink — especially in countries like Japan where fertility has long been below replacement level — it will become much older. By 2100 projections suggest there will be twice as many adults over 80 as there are children under five.

The big picture: The projected population changes won't play out evenly around the world, which means we could well see major adjustments to the international order.

  • China is set to become the world's biggest economy and is challenging the U.S. for international dominance. But decades of enforced low fertility means that China is set to age and then shrink, potentially setting it on a path of decline shortly after the country reaches the peak of its power.
  • Sub-Saharan Africa is projected to escape population decline, which means that what is currently the poorest part of the world is the one that will have a surplus of an endangered resource: working-age adults.
  • The U.S. is expected to be more resistant to decline than most developed nations, with a population in 2100 projected to rise just slightly higher than current levels. But it will be much older, and those numbers could be skewed if immigration — the main source of growth going forward — is further curtailed.

Yes, but: These projected population declines are in some ways a measure of global success.

  • As countries have grown richer and, especially, as women have become freer and more educated, fertility rates have fallen around the world.
  • A smaller human population should slow the effects of climate change, though it's important to remember that wealth has a much bigger effect on carbon emission than sheer numbers.

The catch: Any forecast that attempts to peer 80 years into the future inevitably rests on assumptions that may be — and almost certainly are — flawed.

  • The UN's latest projections, for instance, are for global population to reach nearly 11 billion by 2100.
  • While economic power has chiefly been driven by large, working-age populations in the past — hence the demographic dividend that has powered growth in parts of Asia and Latin America in recent decades — there's no guarantee that will continue in the future.
  • AI could help economies get far more out of a shrinking population — or possibly, dispense with the need for workers altogether.

The bottom line: By the time my 3-year-old reaches his grandparents' age, the world could be a lonelier place — and a much different one as well.

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