Dispelling Demographic Delusions

Presented by Dr. Jane O’Sullivan

Recently, the UN has been revising the peak world population downward despite revising recent growth upward. Other demographic groups project even lower peaks. All have been overestimating fertility decline and underestimating population growth so far this century. The delusion that the peak is already baked into the pie downplays the need for greater family planning efforts. Over-optimistic projections are in danger of becoming self-defeating prophesies, as complacency leads to even greater population overshoot.

Featured in our December 2023 magazine issue, Dr. O’Sullivan highlights her research and challenges the prevailing consensus on future fertility trends. Her research examines the realism of optimistic projections, particularly in high-fertility countries. Contrary to demographic expectations, recent trends indicate a departure from the anticipated decline in birth rates, defying the modeling applied to countries that were early adopters of family planning.

Presentation Date: February 22, 2024

Dispelling Demographic Delusions – Presented by Dr. Jane O’Sullivan

Dr. Jane O’Sullivan

Honorary Senior Research Fellow, University of Queensland

Dr. Jane O’Sullivan is an Honorary Senior Research Fellow at the University of Queensland in Brisbane, Australia, an Executive Member of Sustainable Population Australia, and a Co-convener of The Overpopulation Project.

Trained as an agricultural scientist, she has led international research on tropical root crops in subsistence and semi-subsistence farming systems in the Pacific and Southeast Asia, before shifting her focus to the threats posed by population growth to food security, economic development, and ecological sustainability, and the effectiveness of measures available to limit population growth.

Associated Papers:


Questions from audience, with responses from Dr. Jane O’Sullivan and Marian Starkey

When is the world population projected to peak, and at what number? Why do so many people assume there WILL be a population peak?

Dr. O’Sullivan: There is no scientifically robust answer to the question of when, exactly, the world population will peak. There WILL be a population peak, because Planet Earth can’t support an infinite number of humans. When it is “projected to peak” is only relevant if we manage to get birth rates down enough before environmental limits start increasing the death rate. None of the projections have the capacity to anticipate the latter. So it is a game of Russian Roulette to keep letting population grow without taking the actions we need to end growth sooner.

Marian: Yes to everything Dr. O’Sullivan said above, but if you’re just wondering when the United Nations Population Division projects that the population will peak, it’s in 2086, at 10.4 billion (medium projection). Demographers at the UN have projected, with 95% confidence, that the population will be between 8.835 million and 12.412 million in 2100 —where we land within that 3.5 billion range will depend on our level of investment in family planning between now and then.

When is the U.S. population projected to peak, and at what number?


  • New projection (2023)
    • The population for the middle series increases to a peak at 370 million in 2080 and then begins to decline, dropping to 366 million in 2100.
      • The high-immigration scenario increases every year and is projected to reach 435 million by 2100.
      • The low-immigration scenario is projected to peak at around 346 million in 2043 and decline thereafter, dropping to 319 million in 2100.
    • Previous projection (2020)
      • The United States is projected to grow by nearly 79 million people in the next 4 decades, from about 326 million to 404 million between 2017 and 2060. The population is projected to cross the 400-million mark in 2058.

Dr. O’Sullivan: For low fertility countries that are growing through excess net migration, when they peak depends almost entirely on the political response to immigration. Consequently, all projections are politicized.

It’s interesting that the more recent projection revises immigration downwards considerably. That suggests that public sentiment is hardening against high immigration. But it doesn’t constitute evidence that immigration will actually be reduced. The demand for migration from less developed countries, particularly in Africa, the Middle East, and South Asia, is rising steadily. For any developed country to avoid levels of population growth that exacerbate income inequality and erode their welfare systems, they will need to tighten their borders. Some people might consider that a callous response — that we should be prepared to spread the load, and let our standard of living fall until everywhere in the world is the same. I am not taking a position on that, but I would make the observation that overwhelming rich countries with extra people is not really helping people in poor countries. The rhetoric promoted to get people to accept high immigration inevitably denies negative impacts of population growth, and consequently undermines political will for family planning programs in high fertility countries. So, our generosity might ultimately make the situation worse. We can best help people in poor countries by embracing our own population peak and decline and helping them to follow suite.

What might be the reason for the unwarranted optimism regarding population decrease at the UN and other demographic agencies? In your opinion, what’s the benefit to the UN and other organizations in denying the message in the data?

Dr. O’Sullivan: Accepting the message in the data means accepting that the policy shift effected since 1994 was a failure. Over the 30 years since the International Conference on Population and Development (ICPD), not only has UNFPA’s position changed, but its staff have turned over, and the people recruited, at least those whose voices we hear, are strong proponents of the ideology that all population concerns are a threat to women’s rights. It is a threat to their world view and their personal identity to question that position. I think that is why they make sure that policy reviews don’t include any opportunity to ask questions that would reveal these failings. Measuring success is narrowly channeled into metrics such as infant mortality, percentage of births attended by trained midwives, teen pregnancy rates, etc. Rates of fertility decline and population growth are not on their agenda. But the reality of population pressure keeps imposing. So, they welcome any projection that says population growth is going to end lower and sooner than previously thought, and are skeptical about any projection that says it will grow more than previously thought. This is a classic case of motivated reasoning — people believe what they want to believe, what is most self-affirming for their existing position.

Why is the UN changing its attitudes toward the benefits of family planning?

Dr. O’Sullivan: The UN still very much supports family planning as an individual right, and works to improve the quality and accessibility of services. What they have virtually ceased doing is encouraging countries to reduce their population growth. They claim that reproductive health services, of which family planning is only one component, should be provided for the sake of women’s health and rights — and for no other reason. However, this is not as motivating to the governments of poor countries as saying they need to provide it for the sake of economic development, which was the message in the 1970s. Why they shifted position so completely is an open question. I believe the Catholic Church had a significant influence in both undermining the consensus around population growth being harmful to development and escalating hysteria around cases of coercive birth control to make it seem like all national programs that had a population control intention inevitably resorted to coercion.

On development, UNFPA is running a nuanced line, based on the theory of the Demographic Dividend: that reducing the proportion of children (by extending family planning access and avoiding unwanted births) will provide economic stimulus by having a higher proportion of economically active adults. This is a theory with not much empirical backing, since all these countries have very high unemployment so it’s unclear how having more jobseekers will help. It’s their way of saying lower birth rates can help the economy without saying population growth will harm the economy. But it has the unfortunate side-effect of making national leaders fearful of demographic aging and “getting old before getting rich,” so they’re scared to reduce fertility too fast or too far.

My analysis finds that it probably has little or nothing to do with age structure, and everything to do with the rate of growth. In my view, it is breaching our duty of care to suppress this information and let countries grow themselves into a Malthusian trap, where hunger or violent conflicts become unavoidable.

Is your research receiving attention from any members or entities within the United Nations?

Dr. O’Sullivan: I haven’t had any communication from people within UNFPA or the UN Population Division.

Given the hugely disproportionate consumption of resources by the U.S., aren’t we still the most “overpopulated” country in the world … even though our fertility rate is one of the lowest?

Dr. O’Sullivan: The U.S. might be among the most “overconsuming” countries in the world, and adding more people who will adopt that lifestyle is certainly bad for the planet. I don’t think I agree that it’s among the most “overpopulated” though, as it has an enormous resource base and is a large exporter of food to the rest of the world. A lot of that food production might not be ecologically sustainable, but it has scope to be improved without being scaled back. However, some water resources are being over-extracted, and climate change is likely to exacerbate that, so some scaling back would be beneficial.

My position is that all countries would benefit from population contraction, whether or not they are fully utilizing their natural resource base. The U.S. is “overpopulated” on the basis that it would be better off with fewer people. But there are a lot of countries I would rank as more overpopulated.

We know there is a strong correlation between personal wealth (and health) and fertility rates, but which is the cause, and which is the effect? Is this a positive feedback mechanism at work?

Dr. O’Sullivan: There is certainly scope for positive feedback, or a virtuous cycle, in which lower fertility enables greater incomes which encourage lower fertility. However, the problem is that countries with high fertility have found it impossible to increase average incomes. The economic drag of rapid population growth is simply too great. No country has achieved rapid fertility decline by getting richer. Even the Middle East oil states, which did get suddenly richer, were slow to reduce fertility. In contrast, all the countries that reduced fertility through family planning programs have got richer after fertility fell sufficiently (generally to below three children per woman).

The link between higher incomes and lower fertility is not always consistent. Once the culture of large families is broken, in some countries very low fertility might be linked to economic insecurity and high cost of living. In contrast, individuals who achieve greater economic security often have more children. Migrants to richer countries often have more children than the average in the country they left (for example, Polish migrants in the UK and Mexican migrants in the U.S.) because they feel they can afford it and that their kids will have opportunities.

What is your go-to argument when confronting the notion that a declining population leads to rapid economic decline? Additionally, how do we address concerns regarding the impact on national economies when populations become disproportionately skewed towards older age groups?

Dr. O’Sullivan: Show me an example — not just an economic model. The models are wrong because they don’t factor in the effect of labor market tightening on workforce participation. Japan is doing better than many other OECD countries in many indicators of welfare. It hasn’t experienced any shrinkage in the proportion of people working. Across the OECD, the same applies: aging hasn’t reduced employment, it reduced unemployment, underemployment, and exploitative employment. In older populations, a bigger share of the tax take will be spent on pensions and aged care — but a smaller share will be spent on infrastructure and education and unemployment benefits and crime and environmental remediation. I looked at the public infrastructure costs required to provide for population growth, which is supposed to remedy the fiscal strains of aging, and found that the extra outlays for infrastructure and education outweighed the avoided spending on pensions, health care, and aged care. It was a case of the cure being worse than the disease. And that’s only looking at the fiscal costs, not the environmental costs and public amenities sacrificed for growth. I explain this in a discussion paper.

To what extent do those in agrarian economies have children in order to have help growing crops and tending animals?

Dr. O’Sullivan: I think that has always been an excuse rather than a reason. Mostly, they have large families because they don’t have any means of not having large families. And, because it’s normal, it’s what people aspire to. Because in the past many children died, having many children was a sign of a family’s success — that they were able to keep them alive. So, naturally, it became something to be admired. Of course, children can be useful extra labor on the farm or in a family business. But if that were rationally analyzed, I don’t think it would offset the diversion of the mother’s efforts to pregnancy and childcare. They can always hire other people’s children if there is work to be done, and probably spend less paying them than they’d spend raising their own. What I mean is that, even if this is a perception of some people, I doubt that it stacks up in economically rational terms.

I think there is a real motivation to have children to provide security in old age. However, one successful child can provide more security than seven who leave the area to seek work elsewhere. I think countries need to consider improving income support for the elderly as part of their strategy to get fertility down. Just as they should consider addressing barriers to women’s economic participation, such as access to bank accounts and owning land, which in some places is still not allowed. All sorts of structures that have evolved as part of the existing culture can be barriers to change.

Has any country or area successfully outlawed child marriage?

Dr. Sullivan: I haven’t looked into that question. It is certainly difficult to eliminate child marriage just by making it illegal. But raising the legal age is clearly beneficial in discouraging it. Also, getting fertility down, so that most girls only have one or no sibling, means that parents invest more in their daughters and are not so keen to off-load them in marriage. So, this is another virtuous cycle.