Global population growth peaked in the 1960s at over 2% per year. Since then, that rate has more than halved, falling below 1%. The world’s population is still growing, but it’s growing more slowly with each passing decade, driven by a combination of rising education levels, wider access to contraception, soaring costs of raising children, and a broad cultural shift toward smaller families and later parenthood.
The Numbers Behind the Slowdown
A population replaces itself when women have an average of about 2.1 children over their lifetimes, a threshold known as the replacement level. More and more countries have fallen below that line. The United Nations projects that global population will continue rising for several more decades, reaching a peak of roughly 10.3 billion people in the mid-2080s before beginning a slow decline. That trajectory is a dramatic change from the mid-20th century, when families of five or six children were common across much of the world and population was doubling in a matter of decades.
Some countries have dropped far below replacement. South Korea recorded a fertility rate of just 0.72 in 2023, the lowest of any nation on Earth. It has since inched up slightly to 0.8 in 2025, but that is still less than half of what’s needed to maintain a stable population. South Korea is an extreme case, but the direction it represents is global.
Women’s Education Is the Strongest Driver
No single factor predicts lower birth rates more reliably than female education. Women who stay in school longer consistently delay childbearing and have fewer children overall. This pattern holds across cultures and income levels. Education changes the equation in several ways at once: it opens career paths that compete with early parenthood, it increases earning potential (raising the perceived cost of stepping away from work), and it gives women more knowledge of and access to family planning.
Large-scale demographic modeling, including a comprehensive analysis published in The Lancet covering 204 countries from 1950 to 2021, identifies female educational attainment as one of the most powerful predictors of how many children women will have. The relationship is so consistent that researchers use education data as a core input when forecasting future birth rates decades out.
Contraception Changed the Default
For most of human history, fertility was something that happened to people rather than something they chose. Modern contraception flipped that dynamic. When women and couples can reliably decide whether and when to have children, birth rates fall. This is not because people don’t want children at all. It’s because the gap between how many children people have and how many they actually want has narrowed dramatically.
Contraceptive met need, the share of women who want to avoid pregnancy and have access to effective methods, is another variable that demographic models consistently rely on to explain fertility trends. As access has expanded across Asia, Latin America, and parts of Africa over the past 50 years, birth rates in those regions have dropped in tandem. Sub-Saharan Africa, where contraceptive access remains lowest, is also the region where fertility rates remain highest.
Parenthood Keeps Getting More Expensive
The financial cost of raising a child has become a major factor in family size decisions, particularly in wealthier countries. In the United States, childcare alone can consume a staggering share of household income. Monthly childcare prices in 2018, adjusted to 2024 dollars, ranged from about $5,940 per year for a school-age child in a home-based setting to over $19,000 per year for an infant in a childcare center. That high end represents nearly one-fifth of a family’s median annual income for just one child, more than the cost of rent in the 100 largest U.S. metro areas.
These costs ripple outward. Research from the U.S. Department of Labor suggests that some mothers leave the workforce entirely because childcare is too expensive, which reduces family income further and makes the prospect of additional children even less realistic. Three-quarters of U.S. counties saw childcare prices increase over a recent five-year period. When you layer on housing costs, student debt, and stagnant wages relative to living expenses, the financial calculus of having multiple children has shifted in ways that would have been unrecognizable two generations ago.
This dynamic is not unique to the United States. Housing costs in cities like Seoul, Tokyo, London, and Sydney have climbed steeply, and young adults in those places frequently cite affordability as a reason they’re delaying or forgoing parenthood.
People Are Having Children Later
The age at which women have their first child has risen steadily for decades. In the United States, the average age of first-time mothers climbed from 21.4 in 1970 to 24.9 in 2000, and then continued rising to 27.5 by 2023. That’s a six-year shift in roughly two generations. The increase has accelerated in recent years: from 2016 to 2023 alone, the mean age at first birth rose by nearly a full year.
This delay matters because biology imposes constraints. Women who have their first child at 28 or 30 simply have fewer fertile years remaining to have second or third children compared to women who started at 21. Delayed childbearing doesn’t always mean fewer children, but at the population level, the correlation is strong. The CDC has documented that the recent increase in maternal age is driven by two simultaneous trends: fewer first births to women under 25 and more first births to women 30 and older.
Urbanization Reshapes Family Life
In agricultural economies, children are economic assets. They work the land, tend livestock, and eventually care for aging parents. In cities, children are economic costs. They need housing, schooling, healthcare, and years of financial support before they become self-sufficient. This fundamental shift in the economic role of children helps explain why urbanization and falling birth rates move together so predictably.
Population density in habitable areas is one of the variables researchers use to model fertility, and for good reason. As countries urbanize, living spaces shrink, commutes lengthen, and the logistical difficulty of raising multiple children increases. Today, more than half the world’s population lives in urban areas, a share that continues to grow. In highly urbanized nations like Japan and South Korea, fertility has dropped to levels that would have seemed impossible a few decades ago.
Child Survival Changed the Calculation
One of the less intuitive drivers of lower birth rates is the dramatic decline in child mortality. When parents could not be confident that their children would survive to adulthood, having many children was partly an insurance strategy. As healthcare, sanitation, and nutrition improved and under-5 mortality plummeted, the need for that insurance disappeared. Parents in countries with low child mortality consistently choose to have fewer children and invest more resources in each one.
Under-5 mortality is another covariate that appears in global fertility models precisely because this relationship is so robust. It creates a feedback loop: lower child mortality leads to lower birth rates, which leads to smaller families with more resources per child, which further reduces child mortality.
Cultural Expectations Have Shifted
Beyond economics and education, there has been a broad cultural transformation in what people expect from life. In many societies, identity and fulfillment are no longer as tightly bound to parenthood as they once were. Career ambitions, personal development, travel, and lifestyle flexibility compete with the desire to raise children. Marriage rates have declined or been delayed in many countries, and cohabitation without children has become far more socially acceptable.
These shifts don’t mean people have stopped valuing family. Surveys in low-fertility countries consistently show that people want more children than they actually have. The gap between desired and actual family size suggests that falling birth rates are driven less by a rejection of parenthood than by practical barriers: cost, time, career disruption, lack of support, and the sheer difficulty of combining modern work life with raising kids. Countries that have tried to reverse the trend through financial incentives, like South Korea, have found that even aggressive pronatalist policies produce only modest results. South Korea’s fertility rate nudged up from 0.72 to 0.8 over two years, still far below replacement.