Falling birth rates pose real challenges—but pushing for more births may deepen demographic and environmental problems.
For much of the twentieth century, policymakers worried that humanity was multiplying too quickly. Books such as Paul Ehrlich’s The Population Bomb warned that population growth would outpace food production and overwhelm the planet’s resources. Governments debated how to slow demographic expansion.
Today, the anxiety has flipped. In countries from Japan and South Korea to Italy and Iran, the concern is no longer that populations are growing too fast, but that they may soon stop growing altogether.
The shift reflects one of the most significant demographic transformations in modern history. According to the United Nations’ World Population Prospects 2024, the global fertility rate has fallen sharply—from about five children per woman in the 1960s to roughly 2.2 today, close to the level required for long-term population stability. Over the same period, life expectancy has increased by more than twenty years.
The result is a world that is still growing—but growing older.
These changes bring real challenges. Aging populations put pressure on pension systems and healthcare infrastructure while reducing the share of working-age adults in many economies. Economists at the International Monetary Fund have warned that declining fertility combined with longer life spans could slow economic growth in some countries by shrinking the labour force.
But recognizing a demographic challenge does not mean every proposed solution will work.
In Iran, as in several other countries experiencing falling fertility, the most common policy response has been the simplest one: encourage people to have more children.
It is an appealing slogan. It is also a misleading one.
A demographic transition decades in the making
Humanity now numbers more than eight billion people. Despite falling fertility rates, the global population continues to grow because people live longer. The United Nations projects that the world population will likely reach around 10.3 billion in the mid-2080s, then stabilize and gradually decline.
That growth, however, will be uneven.
More than half of future population growth is expected to occur in a small group of countries, mainly in Africa and South Asia. Meanwhile, large parts of Europe and East Asia have already entered an era of demographic stagnation.
Across the Organization for Economic Co-operation and Development (OECD), fertility rates in almost every country have fallen below the replacement level of about 2.1 children per woman, the threshold required to maintain a stable population without immigration.
Iran increasingly fits this pattern.
During the 1980s, the country had one of the highest fertility rates in the world—more than six children per woman. But rapid urbanization, expanded education for women, and economic pressures contributed to one of the fastest declines in fertility ever recorded. Today Iran’s fertility rate stands at roughly 1.7 births per woman, according to World Bank estimates.
At the same time, the country’s population is aging. The median age of Iranians is now in the mid-thirties, reflecting a rapid shift from a very young society to a more mature one. This transformation has triggered growing alarm among policymakers. Yet Iran’s demographic transition differs from that of many wealthy aging societies. Japan, Germany, and Italy became rich before they grew old. Iran, by contrast, is aging while still facing persistent economic instability, environmental stress, and a fragile welfare system.
That difference matters.
The limits of pronatalist policy
When governments worry about declining birth rates, they often turn to pronatalist policies—financial incentives, tax benefits, childcare subsidies, or campaigns promoting larger families.
Yet international experience suggests these policies rarely reverse fertility decline.
South Korea offers perhaps the clearest example. Since the mid-2000s, the government has spent more than $200 billion on programs designed to encourage childbirth. Despite these efforts, the country’s fertility rate has continued to fall, reaching about 0.7 births per woman in 2023, the lowest in the world.
Demographers say the reason is straightforward: fertility decisions respond more to social and economic conditions than to financial bonuses.
Research compiled by organizations such as the OECD and Our World in Data shows that birth rates tend to decline when housing costs rise, employment becomes insecure, and childcare responsibilities fall disproportionately on women.
Under those circumstances, financial incentives rarely produce lasting demographic change. Iran faces many of these pressures.
Housing affordability has deteriorated sharply in recent years, inflation remains high, and economic uncertainty has made long-term planning difficult for many households. In such conditions, official calls for larger families often sound detached from the realities facing younger generations.
For many couples, having fewer children reflects not just cultural change but economic caution.
Demography cannot be separated from ecology
Population debates in Iran are often framed in terms of national strength. But demographic policy cannot be separated from environmental and economic realities.
Iran is among the most water-stressed countries in the world. Over recent decades, renewable water resources per capita have declined dramatically due to population growth, groundwater depletion, and climate change. Agriculture faces increasing strain, and several major cities already experience periodic water shortages.
Environmental researchers frequently describe the country as approaching severe water stress, a threshold defined by the United Nations as fewer than 1,700 cubic meters of renewable freshwater per person per year.
Population growth in such conditions is not merely a demographic issue—it is also an ecological one.
Every additional million people requires water, food, energy, housing, and infrastructure. When those systems are already under pressure, demographic policy cannot ignore environmental limits.
Globally, scientists studying sustainability increasingly emphasize that population trends must be considered alongside resource consumption and ecosystem stability. Research on planetary boundaries, led by Earth-system scientists including Johan Rockström, suggests that humanity has already crossed several environmental thresholds linked to climate change, biodiversity loss, and nutrient cycles.
In that context, the question is not simply how many people a country has, but whether the ecological systems supporting them can endure.
Rethinking demographic resilience
Declining fertility does create real policy challenges. Aging societies must rethink how they organize work, care, and economic productivity.
But international experience suggests that adapting to demographic change requires broader strategies than simply encouraging more births.
Countries confronting aging populations increasingly rely on a combination of responses: immigration policies to stabilize labour markets, investments in automation and productivity, expanded care systems for older adults, and pension system reforms.
In other words, the long-term sustainability of a society depends less on the number of children born each year than on the economic and institutional systems that support people throughout their lives.
For Iran, this reality presents a difficult choice.
The country can treat demographic decline as a political slogan and attempt to reverse it through pressure and incentives. Or it can confront the deeper structural challenges—economic insecurity, environmental stress, and weak social infrastructure—that shape demographic behaviour in the first place.
Population is not the real measure of strength
A nation’s strength is not determined simply by how many people it has.
It is determined by whether those people can live healthy, secure, and productive lives.
Clean air. Reliable water supplies. Economic opportunity. Public trust in institutions. Schools that function. Healthcare systems capable of supporting an aging population.
These foundations matter far more than the raw number of births.
History suggests that societies become resilient not by maximizing population growth but by building stable economic and ecological systems in which people can thrive.
For Iran, the real challenge is not simply demographic decline. It is whether the country can create conditions in which bringing new life into the world feels like a hopeful decision rather than a risky one. Encouraging births without addressing those conditions may generate political slogans.
But it will not solve the deeper problem. A sustainable demographic future will depend not on how many children are born, but on whether the society they inherit can support them.