Global population growth is slowing. Here’s a reason why

On November 15th, the number of people on this planet – as estimated by demographers – reached eight billion. Population growth has been constant over the past few decades, with about a billion people being added every ten years. But this pattern is changing. Growth is beginning to slow, and experts predict the world population will peak at around 10.4 billion sometime in the 2080s.

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

This slowdown is in part the result of a shift towards fewer offspring – a phenomenon that is occurring almost everywhere, but at different speeds. High-income countries currently have the lowest fertility rates, and the opposite is true: countries with the highest fertility rates tend to have the lowest incomes. “The gap between wealthy and poorer nations has continued to widen,” says Jennifer Sciubba, a social scientist at Rhodes College who has written about these demographic shifts on a global scale. “But in the long term, we are moving towards convergence.” In other words, the current discrepancy between nations’ birth rates is not a permanent one. It’s a temporary gap that will narrow over the coming decades.

Many factors contribute to the ebb and flow of the world’s population, such as migration, mortality, longevity, and other important demographic metrics. However, the focus on fertility helps illustrate why the total number of people on Earth appears to be declining. Demographers define fertility as the average total number of live births per female in a region or country. (In the accompanying graphs, the term “female” is used to include anyone who was assigned a female at birth.) For example, the current fertility rate in the United States is about 1.7; China’s is 1.2. Demographers consider a fertility of 2.1 to be the reproductive rate—that is, the average number of offspring required for a population to remain stable. Today, birth rates in the richest countries have fallen below the replacement rate. In the coming decades, most other countries in the world are likely to follow. This is what it could look like.

In 1960, when the world population was three billion, almost every country had a fertility rate above 2.1 live births per woman.

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

But in the decades that followed, that began to change. A country’s fertility rate tends to correlate with its median income. Wealthier countries were the first to move toward fewer offspring, but lower-income countries are also following the same trend.

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

Here’s the picture today as we surpass eight billion.

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

From the 1990s to the present, fertility has been particularly disparate in higher- and lower-income countries. But by the end of the century, fertility rates around the world will converge towards lower levels again.

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

These numbers provide insight into how – and where – the population growth rate is changing. But the future of humanity clearly depends on many other things besides fertility. For example, people in wealthier countries may produce fewer children, but those offspring tend to use up more resources — so rich countries, despite their dwindling populations, can still have outsized impacts on the planet. Organizations like the United Nations Department of Economic and Social Affairs – which tracks and predicts population numbers – are working on policy-based solutions for how we can all lead healthy, fulfilling and sustainable lives on earth. A clear understanding of population shifts is critical to achieving that bright future.