The Dynamics of Population Growth and Fertility Rates: A Development Perspective

Every year, headlines warn of a world either growing too fast or shrinking too quickly. In parts of sub-Saharan Africa, women are still having five or six children on average. In South Korea, the fertility rate has dropped to a historic low of 0.7. These are not just demographic curiosities – they are windows into how deeply a country’s development shapes the most personal of decisions: how many children to have. Understanding the connection between population growth and fertility rates is central to grasping why some nations struggle with overcrowded schools and strained hospitals, while others face aging populations and shrinking workforces.

What fertility rate actually means 🔗

Before diving into global patterns, it helps to be clear about what we’re measuring. Total Fertility Rate (TFR) refers to the average number of children a woman would have over her lifetime, based on current age-specific birth rates. As Britannica explains, the single most important factor in population growth is the TFR. If women give birth to an average of 2.1 children and those children survive to adulthood, the population essentially replaces itself – that 2.1 figure is known as the replacement rate.

When TFR stays consistently above 2.1, a population grows. When it falls below, the population eventually shrinks – though not immediately, because of what demographers call population momentum: even after fertility drops, earlier high-fertility periods leave behind large numbers of young people still entering their childbearing years, keeping birth numbers elevated for another generation or two.

As of 2023, global TFR ranged from as low as 0.7 in South Korea to as high as 6.1 in Niger – a striking contrast that captures the enormous disparity between highly developed and least developed nations. The global average TFR has fallen from around 5 in the 1960s to approximately 2.3 today, a dramatic transformation driven by development, education, and access to healthcare.

The demographic transition: how populations change with development 🔗

To understand why fertility rates differ so sharply between rich and poor countries, demographers rely on a foundational framework called the Demographic Transition Model (DTM). First proposed by American demographer Warren Thompson in 1929 and later refined by Frank Notestein in the 1940s, the model describes how societies move from high birth and death rates to low ones as they develop economically.

According to Our World in Data, the key insight of the model is not just that mortality and fertility both fall with development – it’s the timing of those falls that explains population growth. Death rates decline first, thanks to improvements in medicine, sanitation, and food supply. Birth rates take longer to follow. This gap between a falling death rate and a still-high birth rate is precisely when populations explode.

The five stages at a glance 🔗

In Stage 1, high birth rates and high death rates cancel each other out, resulting in minimal population growth. This characterized most of human history before the 18th century. Stage 2 marks the turning point: death rates fall sharply due to improvements in healthcare and sanitation, but birth rates remain high – causing rapid population growth. Countries like Afghanistan, Niger, and parts of sub-Saharan Africa still exhibit Stage 2 characteristics.

In Stage 3, birth rates begin to fall as urbanization increases, women gain more education, and contraception becomes more accessible. Population continues to grow, but more slowly. Most developing countries today are in Stage 3, including large parts of South Asia and Latin America. Stage 4 is characterized by low birth and death rates, a stable population, and a higher proportion of older citizens – typical of Western Europe, Japan, and the United States. A proposed Stage 5 captures countries where fertility has dropped so far below replacement that populations are now declining, with the elderly outnumbering the young.

Why developing regions have higher fertility rates 🔗

High fertility in lower-income countries is not simply a matter of cultural preference. It reflects concrete material and structural realities. In least developed countries, fertility rates remain high partly because families depend on children for labor and for old-age support – a rational response to the absence of pension systems and formal social safety nets. Where child mortality remains high, parents also tend to have more children as a buffer against the risk of losing some of them early.

Beyond economic incentives, access to healthcare and contraception plays a decisive role. According to the UN’s SDG report, as of 2021, approximately 44% of partnered women across 68 countries report lacking the ability to make their own healthcare and contraceptive decisions. This reproductive disempowerment is not just a health issue – it is a development issue that directly drives higher fertility.

The role of women’s education 🔗

One of the most consistent findings in development research is that educating girls is among the most effective ways to lower fertility rates. Educated women generally have fewer children than uneducated women – a relationship that holds strongly across both developed and developing countries. The pathways are multiple: higher education increases the economic cost of time spent on childrearing, improves women’s health knowledge, and empowers them to participate in household decision-making about family planning.

A University of Washington study published in Population and Development Review found that girls’ educational attainment – particularly reaching lower secondary level – significantly accelerates fertility decline in high-fertility settings. In Kenya, as contraceptive prevalence rose from 5% to 51%, the TFR dropped from 7.64 to 4.06 births per woman. The study concluded that family planning and education work together, with contraceptive access having the larger immediate effect, and education shaping long-term aspirations and reproductive choices.

Why developed countries face the opposite problem 🔗

While developing nations grapple with rapid population growth, many wealthy countries face a different demographic challenge: fertility rates too low to sustain their populations. Developed countries tend to have lower fertility rates due to lifestyle choices associated with economic affluence – birth control is easily accessible, and children can become an economic drain due to housing, education, and childcare costs. Women often delay childbearing in favour of higher education and professional careers, further reducing completed family sizes.

By 2005, total fertility rates had fallen to 1.3 children per woman in Italy, Spain, Germany, and Japan – far below the replacement rate of 2.1. This has produced rapidly aging populations, growing pressure on pension and healthcare systems, and concerns about shrinking workforces. Some countries have turned to immigration to offset these demographic deficits, though that too comes with its own policy challenges.

Can policy reverse low fertility? 🔗

Few policy interventions have successfully reversed low fertility rates, though some have shown modest results. France is often cited as a partial success: by expanding childcare, parental leave, and per-child financial subsidies, it managed to raise its TFR from around 1.7 in the mid-1990s to roughly 1.9. An NBER study by Sacerdote, Feyrer, and Stern found that in countries where men take on a greater share of household and childcare responsibilities, fertility rates tend to recover from historic lows – suggesting that gender equity at home, not just in the workplace, is a key lever.

Fertility, healthcare, and economic development: a two-way relationship 🔗

The link between fertility and development runs in both directions. High fertility strains healthcare systems, limits educational investments per child, and slows economic growth. But declining fertility, when managed well, can create a demographic dividend – a window when the working-age population is large relative to dependents, boosting productivity and savings. Countries like South Korea, Taiwan, and Indonesia leveraged this dividend effectively during their periods of rapid growth.

As research published in PNAS notes, when fertility rates decline, children’s health and education tend to improve – parents invest more resources in fewer children. This shift from quantity to quality in child-rearing is one of the foundational changes that drives long-term economic development. Conversely, without fertility decline, rapid population growth can outpace a country’s ability to build schools, hospitals, and jobs fast enough to meet demand.

A large cross-country study in BMC Public Health confirmed that TFR is consistently lower in countries with longer average female education, higher GDP per capita, higher contraceptive prevalence, and stronger family planning programs. This combination of factors – not any single one in isolation – determines where a country sits on the fertility spectrum.

Global population trends to watch 🔗

The United Nations projects that global fertility will continue to decline through the rest of this century and is expected to fall below the replacement level of 1.8 by 2100, with world population peaking around 2084. The most significant population growth in coming decades will be concentrated in sub-Saharan Africa, which remains the highest-fertility region in the world, largely due to slower progress in women’s education and family planning access.

Meanwhile, the experience of East Asian economies like South Korea – where fertility has fallen to levels once thought impossible – signals that development does not guarantee a stabilization of birth rates; it can drive them far below what is needed to sustain a population. This creates a new set of challenges around care for the elderly, pension sustainability, and economic stagnation, even as other parts of the world remain locked in the earlier phases of rapid growth.

Population growth and fertility rates are not standalone statistics – they are reflections of how societies are organized, what opportunities exist for women, how healthcare is distributed, and how much autonomy people have over their own reproductive lives. A development perspective forces us to ask not just “how many people?” but “under what conditions, and with what choices available?”

What do you think? As countries with rapidly aging populations consider pronatalist policies to boost birth rates, should the focus be on financial incentives for families or on structural changes like affordable childcare and shared parental responsibilities? And in high-fertility developing regions, is access to contraception or investment in girls’ education the more urgent policy priority?

References

1. https://www.britannica.com/topic/fertility-rate
2. https://en.wikipedia.org/wiki/Total_fertility_rate
3. https://ourworldindata.org/demographic-transition
4. https://www.buddinggeographers.com/demographic-transition-model-dtm/
5. https://populationeducation.org/what-demographic-transition-model/
6. https://www.sciencedirect.com/science/article/abs/pii/S0738059325000859
7. https://wol.iza.org/articles/female-education-and-its-impact-on-fertility/long
8. https://www.washington.edu/news/2020/09/08/how-birth-control-girls-education-can-slow-population-growth/
9. https://pmc.ncbi.nlm.nih.gov/articles/PMC4255510/
10. https://www.nber.org/digest/dec08/understanding-fertility-within-developed-nations
11. https://www.pnas.org/doi/10.1073/pnas.2110170118
12. https://link.springer.com/article/10.1186/s12889-020-8331-7