Global Population Growth Is Slowing Down. Here’s One Reason Why

Global Population Growth Is Slowing Down. Here’s One Reason Why

In 2022 the world’s population hit the eight-billion mark. But such milestones could top out by the end of the century

Credit: Katie Peek; Source: World Population Prospects 2022, United Nations Population Division

On November 15–as estimated by demographers–the count of humans on this planet reached eight billion. Over the past few decades, population growth has been steady with billion-person marks appearing every dozen years. This is changing. Growth is beginning to slow, and experts predict the world’s population will top out sometime in the 2080s at about 10.4 billion.

Population curve shows a steady increase since 1960, projected to top out at 10.4 billion before 2100.
Credit: Katie Peek; Source: World Population Prospects 2022, United Nations Population Division

This slowdown is partly due to a shift towards fewer offspring, a phenomenon that is occurring almost everywhere, but at different rates. The lowest birth rates are currently found in high-income countries. However, the reverse is true: the highest birth rates lead to lower incomes. Jennifer Sciubba, a Rhodes College social scientist, says that the gap between rich and poor nations has continued to grow. She has written extensively about these global-scale demographic shifts. “But we’re moving towards convergence” Longer term, this means that the current disparity in birth rates between nations isn’t permanent. It’s temporary and will shrink over the next decades.

Major demographic factors, including migration, mortality, and longevity, all contribute to the world’s population fluctuations. However, focusing on fertility can help to explain why the number of human beings on Earth seems to be falling. Demographers define fertility to be the average number of live births per woman in a given region or country. In the accompanying graphics, the term woman is used to refer to anyone who was born as a woman. For example, the U.S. has a fertility rate of 1.7 while China’s is 1.2. Demographers consider a fertility rate of 2.1 the replacement rate, which is the minimum number of offspring required for a population to remain stable. Today, the replacement rate is lower than the birth rates in the richest countries. Most countries around the globe will follow the example of the wealthy over the next decades. Here’s what that might look like.

In 1960, when the world’s population was three billion, nearly every country had fertility rates above 2.1 live births per woman.

Chart shows fertility rates for 217 regions in 1960, color-coded by income. All but 5 exceed the replacement rate of 2.1.
Credit: Katie Peek; Source: World Population Prospects 2022, United Nations Population Division

But that started to change over the following decades. The fertility rate of a country is usually correlated with its average income. While wealthier countries were the first to adopt a trend toward fewer offspring than their average income, lower-income countries are also following this trend.

Charts break down falling fertility rates from 1974 to 2010. By 2010, most high- and high-mid-income regions were below 2.1.
Credit: Katie Peek; Source: World Population Prospects 2022, United Nations Population Division

Here is the picture as we reach eight billion.

By 2022, birthrates in Hong Kong and South Korea dipped below one baby per woman. The U.S. rate is currently 1.66.
Credit: Katie Peek; Source: World Population Prospects 2022, United Nations Population Division

Fertility was especially different in higher- and lower-income countries from the 1990s through today. However, by the end century, fertility rates will be lower worldwide.

Charts show projected fertility rates. By 2058, about one quarter of regions are projected to have above-replacement levels.
Credit: Katie Peek; Source: World Population Prospects 2022, United Nations Population Division

These numbers give insight into how and where the population growth rate is changing. Humanity’s future depends on many other factors than fertility. People in wealthier countries may have fewer children but their offspring tend to use more resources. This means that rich countries can still have large planetary impacts despite having fewer people. Organizations like the United Nations Department of Economic and Social Affairs, which tracks and predicts human populations, are working towards policy-based solutions to ensure that everyone can live healthy, fulfilling and sustainable lives. It is crucial to have a clear understanding of the population shifts in order to achieve a bright future.

ABOUT THE AUTHOR(S)

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    Katie Peek is a science journalist and data-visualization designer with degrees in astrophysics and journalism. She is a contributing artist for Scientific American. Credit: Nick Higgins

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