Population collapse is a far greater risk to civilisation than climate change, according to Elon Musk. Never afraid to share his opinions, the tech billionaire posted the claim on Twitter (now X) in May 2022. Since then, he has focused on how SpaceX can send people to Mars, which may not help with earth’s numbers, or its ability to take care of them.

Buried in the hyperbole is a question that some of the world’s most rigorous demographic researchers have been asking for decades, and one that is becoming increasingly difficult to ignore.

What happens when a society can no longer replace itself?

It is not a hypothetical. According to South Korea’s Ministry of Data and Statistics, the country’s total fertility rate – the average number of children a woman can expect to have in her lifetime – fell to 0.72 in 2023, the lowest ever recorded for any country. A rate of 2.1 is needed to maintain population stability. Japan’s sits at 1.2 and has been below replacement since the early 1970s. In Europe, Italy recorded just over 350,000 births in 2024, compared to more than one million in 1964. Three births then for every one now. The largest single age group in Italy today is people born sixty years ago.

The Slow Hand of the Clock

Francesco Billari has spent his career thinking about the future through the lens of the present. As Professor of Demography and Rector of Bocconi University in Milan, he leads one of Europe’s most internationally respected academic institutions while being among the world’s foremost scholars of fertility and population change.

Billari draws on an analogy from Alfred Sauvy, the great 20th-century demographer commissioned by de Gaulle to establish France’s national demographic institute. A fine watch has three hands, Sauvy observed: the fast-moving second hand of politics; the slower minute hand of economics; and the nearly imperceptible hour hand of demography. You cannot see it move, but it is telling you something definitive about the future.

In Billari’s reading, we inhabit a world of historically unprecedented demographic conditions. “At the global level, we live in an era of highest life expectancy, lowest fertility, highest population ageing and slow population decline in some parts of the world. For the first time in history, we have several generations living together and several populations living together and also a high rate of migration between these populations,” he shared in an interview with Alain Elkmann last month. It is an experiment with no historical precedent.

Adding to such turbulence, Francesco Billari has expressed concern that Europe’s sustained low fertility rates are creating unprecedented demographic pressures. While it can be argued that migration provides a counterforce to ageing populations, he believes that over-reliance on it will not solve the issues facing society. Migration flows, he points out, are driven by volatile short-term factors such as economic crises and political upheaval rather than the stable, long-term patterns needed to substitute for structural fertility decline. The numbers simply do not work as a permanent fix.

The Parenting Arms Race

Understanding why birth rates have fallen requires looking not just at economics or policy, but at something more intimate: what it now means, socially and psychologically, to be a good parent.

A landmark study published late in 2025 in the Brookings Papers on Economic Activity offers a striking answer. Research by Professor Michèle Tertilt of the University of Mannheim and her colleagues Professor Minchul Yum and Dr. Lukas Mahler shows that parents would often like to have more children, but choose not to because they feel they cannot keep up with other parents and their investments in education, tutoring, and childcare.

The economists argue that not only financial burdens or a lack of childcare facilities play a role, but above all social pressure to make exceptionally high investments for each individual child – in education, extracurricular activities, or private tutoring. Fewer children, more invested in each. The result is a shrinking society whose remaining members are intensively cultivated.

One mechanism driving this pressure is the expanding influence of social media, particularly “momfluencers” who present idealised images of modern motherhood on platforms such as Instagram and TikTok: creative early education, home-cooked organic food, perfectly designed nurseries. The benchmark for adequate parenting has been raised, and made visible in real time.

The Mannheim team’s economic model reveals a self-reinforcing dynamic. The greater the social comparison, the higher the investment pressure per child and the lower the birth rates. This correlation is visible within countries as well as between them: in regions of the US with high levels of social networking, the number of children is particularly low even among comparable income groups, while in less socially competitive rural regions, birth rates are higher at equivalent income levels.

The pressure is particularly acute in societies with high-stakes examinations – school systems where test results are decisive for school careers and future opportunities, as in South Korea and the United States. South Korea, the world’s fertility outlier, is also home to one of the world’s most ferociously competitive educational cultures. These are not coincidental data points.

What Collapse Actually Looks Like

Demographers are careful with the word collapse. But they are also honest about what sustained below-replacement fertility means over time, especially when no compensating mechanism is in place.

The most immediate consequence is the inversion of the age pyramid. Instead of a broad base of young workers supporting a narrower tier of retirees, ageing societies increasingly face the reverse: a shrinking working-age population carrying an expanding burden of elderly dependents. Pension systems designed for different demographic assumptions become fiscally strained. Healthcare systems face exponentially growing demand from older populations at precisely the moment the workforce paying for them is contracting.

One response, pursued aggressively across East Asia, BIllari notes, is to compensate for fewer young people through higher investment in each, expanding their education and increasing their human capital. Japan, Korea, and China are all doing this. The Korea Times reports that private education spending has surged by over 60% in the past decade.

The logic is sound as far as it goes. If you cannot have more workers, make each worker more productive. But this approach has limits, and it interacts uncomfortably with the Mannheim findings. Intensive parenting is simultaneously a rational response to demographic decline and one of its causes.

The economic consequences are not confined to pensions. Consumer economies depend on growth, and growth depends on population expansion, or at least stability. Housing markets, urban infrastructure, healthcare capacity, defence – virtually every major planning assumption in modern states has population growth baked into it somewhere. Japan has spent thirty years learning, slowly and painfully, how to rethink these assumptions. Much of southern and eastern Europe is only beginning.

The Question of Recovery

The Rector of Bocconi University is not a fatalist. His 2023 book Domani è Oggi – Tomorrow is Today – argues explicitly that demographic futures are shaped by today’s choices. Policy can, for example, make factors like migration work to better support – not fix – economy and society. “Countries such as Germany, Canada, and Australia have maintained economic dynamism thanks in part to their ability to attract and integrate skilled migrants,” Billari shares in a recent op-ed, pointing out why a zero-migration policy can have damaging consequences. “Those who close themselves off in a demographically restricted world risk reducing their productive and fiscal base just as the burden of pension and healthcare spending increases.”

Policy too can shift fertility norms, and there is evidence it has done so. France and the Nordic countries have maintained fertility rates significantly above the European average, at least in part through sustained family policy: generous parental leave, affordable childcare, cultural normalisation of dual-income households.

The Mannheim team points toward a complementary set of levers. Reforms to examination systems, expansion of public education and tutoring services, and open social conversation about what constitutes a reasonable level of parental investment could all contribute to reducing competitive pressure and making parenthood a more accessible choice.

There is no quick solution. Demographic change is the slow hand of the clock. If South Korea’s fertility rate recovered to replacement level tomorrow – a scenario with no basis in current evidence – the population effects would not be fully felt for decades. The children not born in the 1990s and 2000s are not available to have children now.

A Question of Civilisational Confidence

There is something deeper beneath the data. Fertility rates are, among other things, a measure of confidence – in the future, in institutions, in the idea that bringing a child into the world is an act of hope rather than recklessness. When that confidence erodes, it shows up in the numbers long before politicians notice.

Musk’s 2022 warning was clumsy and politically loaded, but the underlying anxiety is shared by serious researchers across the ideological spectrum. Billari has noted that population questions are inherently politically awkward, sitting uncomfortably across conventional left-right lines and resisting simple solutions. That awkwardness has led to decades of under-investment in the research and policy capacity needed to address them.

The numbers, however, are not waiting for political convenience. In Italy, three births occurred in 1964 for every one birth in 2024. In South Korea, the fertility rate is less than a third of what is needed for replacement. In Japan, the population is already declining in absolute terms. These are not warnings. They are the arrival of consequences that demographers have been forecasting for a generation.

The slow hand has moved. Will societies act before time runs out?

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