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Maria Blumetti, one of the few female residents left, sits on a bench outside her home on February 19, 2021 in San Paolo Albanese (Potenza), southern Italy.

Every ten years, the U.S. government spends billions of dollars conducting a census to collect information on every person in the United States. The Census Bureau mails questionnaires to U.S. citizens, does some good old-fashioned door knocking, and uses the results to make myriad decisions ranging from hospital locations to congressional representation.

The census process can reveal interesting demographic shifts. The 2020 Census surfaced one particularly noteworthy trend: the U.S. population is growing at its slowest rate since the Great Depression. That finding raised alarm because slowing population growth can cause economic stagnation and, with it, diminished standing in the word. But the United States is not alone in facing this challenge. Population-growth rates are falling in many of today’s largest economies. 

This lesson explores the drivers of population growth, details how population trends affect countries, and examines how governments are responding to slowing growth.  

What drives population growth and decline?

Three factors influence population: births, deaths, and migration. Of course, giving birth, dying, or moving to another country are deeply personal and life-changing moments for individuals and their families. Although totaling up such events into a handful of statistics seems impersonal, policymakers have to do just that, because those statistics can have profound effects on a country as a whole.  

For much of human history, population sizes were relatively stable because deaths were so frequent that people could barely have children fast enough to sustain growth. But the mortality rates, or the proportion of people who die in a year, in many countries began to decline during the Industrial Revolution due to advances in hygiene, infrastructure, and vaccinations. Major developments in health care starting in the twentieth century also resulted in longer and healthier lives. Those gains set off a period of exponential global population growth, with global life expectancy skyrocketing from just thirty-two years in 1900 to over seventy today.
 

Fertility rates, the average number of births per woman over her lifetime, also affect population growth rates. An average fertility rate of 2.1 is known as replacement-level fertility and results in a population remaining unchanged; rates above or below 2.1 drive population growth or decline.

Today, global fertility rates are declining. In the 1960s, the average world fertility rate was nearly five children per woman; in 2019, the rate was 2.4 children per woman. This is largely a result of increased access to contraception and abortion, allowing people greater control over the number of children they have. Women’s increased participation in the economy has also led to a decline in fertility rates. In the United States, for example, women entered the workforce in great numbers in the mid-1900s, with many either delaying or opting out of having children as a result. Fertility rates also decreased as death rates fell among children. In 1950, over a quarter of children worldwide died before reaching the age of fifteen. By 2017, that number had dropped to under 5 percent, which meant fewer people were creating large families in anticipation of some of their children dying.
 

Before the 1950s, not a single country reported a fertility rate below replacement level. Today, eighty-three countries have fertility rates below replacement level, with highly industrialized and wealthy countries such as Malta, Singapore, and South Korea among the lowest. Experts expect that trend to continue: they predict that, by 2100, twenty-three countries—including major economies such as Italy and Japan—will see their populations halve.

As fertility rates have declined, migration has become a more significant influence on population. For instance, in the European Union (EU) as a whole—where deaths have exceeded births since 2012––population growth has been fueled entirely by immigration. Still, in some EU countries like Bulgaria, where the population has fallen by 11 percent the past decade, population size is in decline due to low birth rates and emigration.

Also noteworthy is that, although average global population-growth rates are slowing, some countries are forecasting significant population booms over the next few decades. They expect that growth to take place largely in sub-Saharan Africa, in countries such as Democratic Republic of Congo, Nigeria, and Tanzania. In fact, population experts predict that half of the world’s babies will be born in Africa by 2100.
 

How does population size and growth affect society?

Population size can have a major effect on a country’s economy. At the most basic level, a larger population means more workers and more consumers, which can boost a country’s gross domestic product (GDP). For example, in the United States, which has one of the world’s largest populations, the country’s sizeable citizenry is a main driver of economic prosperity. Meanwhile, a small or declining workforce can stunt GDP growth.

However, population size is just one of many factors that can influence countries’ economies. India’s population is over four times that of the United States, but the U.S. economy is seven times larger than India’s. India’s economy is smaller due to years of colonial exploitation, among other reasons.

Population growth rates also determine the age distribution of a population—another important factor related to economic growth. 

Nearly all countries are experiencing population aging, or a rise in the average age within a population. The most common cause is a combination of fewer births and longer lives. Although longer life spans can seem favorable, they can also pose challenges to policymakers thinking about economic growth. 

Most notably, a large population of nonworking people—e.g., the elderly—places an increased economic burden on working-age people. For instance, workers pay the taxes that fund social security programs that support nonworking people. With a relatively smaller workforce or a relatively larger elderly population, comes the risk that social safety nets will receive inadequate funding. Additionally, younger workers often support and care for older, nonworking family members directly. Such support can significantly strain a worker’s, especially because elderly people are living longer after retirement. An aging population with relatively few young people can also create challenges to military readiness, another measure of geopolitical power.

Because GDP and economic strength are significant indicators of a country’s prosperity and influence in the world, governments go to great lengths to monitor and shape population trends to avoid threats to growth. 

How do countries respond to slowing population growth?

Many countries are implementing policies to offset slowed population growth and mitigate unfavorable population trends. Here’s how six countries have sought to manage their populations’ size. 

From 1980 to 2016, China imposed a one-child policy, which slowed population growth as the country modernized. In 2016, China moved to allow its citizens to have two children. Today, China faces a threat to future economic growth because of its aging population. Consequently, in 2021, China announced that families are permitted to have three children.

Japan has also taken a hands-on approach to dealing with its dismal population-growth rate, enacting several programs that provide incentives and support for new parents. Such policies include mandating twelve-month parental leave, offering direct financial aid to parents, and investing heavily in subsidized childcare. The Japanese government has even backed an artificial intelligence matchmaking service to increase its birth rate. 
 

Many other countries have also enacted parental assistance programs to ease financial burdens, but some experts argue that broader societal issues related to child-rearing also need to be addressed. Those include outdated gender norms [PDF] that can force women to compromise their careers to raise children and, in certain countries, people of color and poorer people facing extra hurdles to raising children.

Some countries, such as France and the Netherlands, have confronted longer life expectancies and slowing population growth by extending the retirement age or the age at which people are eligible for pension benefits. Those increases, however, have been controversial, sparking intense protests and heated debates over fairness and workers’ rights. Meanwhile, Australia, Canada, and other countries have adopted more open immigration policies to counter labor shortages due to their declining populations.

In the coming decades, many more countries will need to consider pursuing such policies or turn to other tools that can influence births, deaths, and migration in their countries. Studies differ about the exact timeline, but most scholars think the population will peak in the late twenty-first century before declining. However, every country is on a different path, and many are experiencing population-related harm to their economies, social security programs, and geopolitical influence now. The changing shape of a population can have far-reaching consequences—so policymakers should watch the shifts in their populations closely. 

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