Humanity may have quietly crossed one of the most consequential demographic thresholds in its history. New research suggests global fertility has fallen below replacement level for the first time potentially bringing the peak and eventual decline of the world's population decades closer than current United Nations projections suggest.
INR Report: Based on reporting by RT, World faces historic population decline – study, published 25 August 2026, examining the research paper Terra Incognita: The Economics of a Shrinking World by economists Jesús Fernández-Villaverde and Patrick Norrick.
The world is still adding people.
But underneath that headline number, something much more fundamental may have changed.
Researchers Jesús Fernández-Villaverde of the University of Pennsylvania and Patrick Norrick of Northwestern University estimate that global fertility is now no higher than 2.19 children per woman.
Their estimated global replacement threshold is approximately 2.2.
If those estimates are correct, humanity has crossed below the fertility level required for each generation to replace itself in the long run.
The researchers describe the significance starkly: humanity is likely below replacement fertility in 2026, something they say has not previously occurred globally — including during major wars and pandemics. (marginalrevolution.com)
That does not mean the world's population begins falling tomorrow.
But it could mean the demographic machinery that eventually produces population decline has already started moving.
The World Could Peak Much Earlier
The new research challenges one of the most important assumptions underlying conventional global population forecasts.
The world's population passed eight billion in 2022 and is currently around 8.3 billion. Existing large generations mean births can continue exceeding deaths for decades even after fertility falls below replacement.
This phenomenon — population momentum — explains why falling fertility does not immediately translate into falling population.
But Fernández-Villaverde and Norrick estimate that this momentum may sustain growth for only another three decades.
Their analysis points towards a world population of roughly nine billion around 2056, followed by decline. That contrasts sharply with the United Nations' 2024 medium projection, which puts the peak at approximately 10.3 billion in the mid-2080s. (intellinews.com)
That is not a minor disagreement.
It potentially moves the demographic turning point forward by around 30 years and lowers the peak by more than a billion people.
Which projection proves closer to reality will depend heavily on what happens to fertility over the coming decades.
Fertility Is Falling Almost Everywhere
Perhaps the most significant finding is that falling fertility can no longer be dismissed as primarily a European, Japanese or wealthy-world phenomenon.
The researchers examined 236 countries and territories between 1950 and 2023.
Fertility declined in 219 of them.
Their modelling found the common global fertility component peaked in 1978, while country-specific fertility trends are now overwhelmingly negative — with the researchers finding little evidence that those trends are naturally stabilising. (marginalrevolution.com)
The figures cited by RT illustrate how widespread the change has become.
Thailand's fertility rate was estimated at just 0.87 in 2025, Colombia at 1.01, Iran at 1.35 and Brazil at 1.52.
Those are not countries following identical economic or political models.
That creates one of the central puzzles in the research.
Why Are People Having Fewer Children?
There is no shortage of explanations.
Housing affordability.
Childcare costs.
Economic insecurity.
Later marriage.
Greater female participation in higher education and employment.
Urbanisation.
Contraception.
Changing attitudes towards marriage and parenthood.
The researchers do not argue these factors are irrelevant.
Their problem is that no single conventional explanation appears capable of accounting for the scale and geographical breadth of the decline.
Their broader conjecture is provocative: modernity itself may contain powerful incentives towards smaller families.
The economic and lifestyle cost of another child can be substantial, while remaining childless or having only one or two children has become socially and economically much easier.
And fertility has an unusual mathematical characteristic.
Children come in whole numbers.
A relatively modest shift in the proportion of women having three children, two children, one child or none can therefore move a country's average fertility rate surprisingly quickly.
More importantly, there is no obvious economic mechanism automatically forcing fertility back towards replacement once it falls below it. (marginalrevolution.com)
New Zealand Is Already Well Below Replacement
This is not a distant demographic problem for New Zealand.
We are already living it.
Stats NZ says New Zealand's total fertility rate fell from 1.87 births per woman in 2016 to 1.55 in 2024.
For comparison, through most of the four decades from 1976 to 2015, New Zealand's fertility rate generally remained between 1.9 and 2.2.
Stats NZ's latest national population projections assume a median fertility rate of approximately 1.59 in 2025, gradually declining towards 1.55 by 2054 and beyond. (datainfoplus.stats.govt.nz)
That places New Zealand substantially below the roughly 2.1 births per woman generally required for long-term replacement in a developed country without migration.
The decline also isn't merely a statistical consequence of women postponing childbirth.
Stats NZ says completed family size has been falling across generations.
Women born in the early 1950s averaged approximately 2.5 children over their lifetimes.
For women born in the early 1970s, that had fallen to around 2.1.
Census data also indicates increasing levels of childlessness. (datainfoplus.stats.govt.nz)
New Zealand Births Are Falling Again
The latest registration figures provide another indication of the direction of travel.
There were 56,268 live births registered in New Zealand in the year ended June 2026, down from 58,365 in the previous June year.
Stats NZ says that was the lowest number of registered births since 2003. (stats.govt.nz)
The comparison becomes more significant when population growth is considered.
New Zealand's population today is considerably larger than it was in 2003, yet the absolute number of births has returned to levels not seen for more than two decades.
This doesn't establish that births will continue falling every year — fertility can fluctuate considerably — but the longer-term trend identified by Stats NZ is unmistakable.
Immigration Changes the Equation — But Not Fertility
New Zealand has one demographic lever that can delay or offset population decline:
immigration.
Stats NZ's latest projections make that explicit.
The agency's median projection assumes annual net migration gradually increases from around 30,000 in the June 2026 year to 37,500 in 2031, 42,500 in 2051 and approximately 49,250 by 2078.
Across the projection period from 2025 to 2078, that represents a direct population gain from net migration of approximately 2.28 million people. (datainfoplus.stats.govt.nz)
That distinction matters.
Immigration can increase New Zealand's population and workforce.
It cannot change the underlying fertility rate of the existing population.
A country can therefore simultaneously experience very low domestic fertility and continuing population growth.
For policymakers, those are two different demographic questions and arguably should be discussed separately.
What Happens When Every Generation Gets Smaller?
Low fertility is initially easy to overlook because its effects unfold slowly.
There are fewer babies.
Several years later, there are fewer schoolchildren.
Two decades later, fewer young people enter the workforce.
Eventually, fewer workers support a growing population of retirees.
The global study warns that shrinking younger generations could place increasing pressure on pension systems, healthcare, government finances and economic growth.
Its authors illustrate the economic arithmetic using the United States: if productivity increased by 2% annually while the workforce contracted by 0.5%, long-term GDP growth would fall towards approximately 1.5%.
Population decline therefore does not necessarily mean declining living standards.
If productivity rises sufficiently quickly, GDP per person can continue increasing even while the population and workforce shrink.
But it changes the equation substantially.
Economic growth becomes increasingly dependent upon productivity rather than simply adding more workers and consumers.
For New Zealand — which has struggled with productivity growth for decades — that distinction deserves considerably more attention.
The Ageing Problem Comes First
Population decline itself may be decades away in many countries.
Population ageing arrives first.
When fewer children are born while people live longer, the proportion of older citizens increases relative to the working-age population.
That changes government finances.
Superannuation and healthcare spending tend to increase while the relative pool of workers financing those systems through taxation becomes smaller.
New Zealand's own population projections already incorporate this ageing process.
The policy challenge therefore isn't simply:
How do we keep the population growing?
It is also:
How does a smaller proportion of working-age New Zealanders support a larger retired population?
Those are not necessarily the same problem.
Can Governments Reverse Falling Fertility?
Governments around the world are already trying.
Russia, for example, has introduced childbirth payments, expanded maternity benefits and family-support programmes. It has revived its Soviet-era "Mother Heroine" award, including financial rewards for women raising very large families.
President Vladimir Putin has repeatedly called for economic and social conditions that make larger families easier to support.
Other countries have tried subsidised childcare, parental leave, housing assistance, tax incentives and direct payments.
There have occasionally been modest fertility rebounds.
But evidence that these programmes can sustainably restore fertility from very low levels to replacement remains limited.
Recent academic analysis notes that countries including Norway, Sweden and France experienced temporary rebounds following family-support policies, while Russia, Hungary and Poland have also recorded periods of improvement after pronatalist programmes.
The longer-term global trend, however, remains downward. (tandfonline.com)
Elon Musk Calls It an Existential Problem
The study also attracted the attention of Elon Musk, who has warned repeatedly about declining birth rates.
Responding to discussion of the new research, Musk wrote that he had been warning about the issue for years.
He has previously described low fertility as a potentially greater long-term threat to civilisation than climate change and has argued that population decline should be treated as a major policy issue.
Musk's rhetoric is deliberately dramatic.
But the underlying demographic trend is no longer particularly controversial.
The argument is increasingly about how quickly fertility is falling, where population will peak and what happens afterwards.
Does This Affect New Zealand?
Yes — directly.
New Zealand's fertility rate has already fallen to around 1.55, far below replacement, while the latest year to June recorded the country's lowest number of registered births since 2003. (stats.govt.nz)
That does not mean New Zealand's population is about to collapse.
Migration can sustain population growth for a considerable period, and Stats NZ explicitly incorporates substantial future net migration into its population projections. (datainfoplus.stats.govt.nz)
But immigration does not remove the underlying demographic question.
If New Zealand-born generations become progressively smaller, policymakers eventually face choices about workforce size, immigration, infrastructure, housing, productivity, taxation, healthcare and superannuation.
There is also a more fundamental question that economics alone cannot answer.
Why are New Zealanders having fewer children?
If the answer is simply changing personal preference, governments may have relatively little reason — or ability — to intervene.
But if New Zealanders want children and are having fewer than they would prefer because housing, family formation, childcare costs or economic insecurity make parenthood increasingly difficult, then low fertility becomes a legitimate public-policy issue.
Stats NZ itself identifies housing, childcare, education, employment patterns, partnership stability, family preferences and government policy among the factors that could influence future fertility. (datainfoplus.stats.govt.nz)
That makes fertility more than a population statistic.
It becomes another measure of whether younger New Zealanders believe they can afford to build the lives and families they want.
And if the new global research is correct, New Zealand isn't confronting this question alone.
For the first time in human history, the entire world may be entering the same demographic experiment.
We know how economies work when each generation is larger than the last.
We are about to discover what happens when it isn't.
Source: RT — World faces historic population decline – study, published 25 August 2026. Based on Terra Incognita: The Economics of a Shrinking World by Jesús Fernández-Villaverde and Patrick Norrick. New Zealand fertility and population projections sourced from Stats NZ. (datainfoplus.stats.govt.nz)
Independent reporting. Original context. Credited sources.