How much does global population decline matter? (with Dean Spears)

Jul 23, 2025 Episode Page ↗
Overview

Dean Spears, an economic demographer at the University of Texas at Austin, discusses global depopulation, low birth rates, and the urgent need for global population strategies. He explores the economic and societal implications of a shrinking population and challenges common misconceptions about its causes and solutions.

At a Glance
11 Insights
1h 7m Duration
19 Topics
5 Concepts

Deep Dive Analysis

Introduction to Global Depopulation and Historical Context

Understanding Replacement Birth Rates and Current Global Trends

Impact of Fewer Children vs. Childlessness on Population Decline

Distinguishing Local Overpopulation from Global Population Trends

Projections for Global Population Peak and Subsequent Decline

Reliability of Demographic Projections and Long-Term Trends

Addressing the 'High Birth Rate Subgroup' Argument

The Importance of a Stabilized Global Population

Economic Benefits of Population: Ideas, Progress, and Knowledge

Economic Benefits of Population: Fixed Costs and Demand

Aging Populations and Economic Adjustments

Exploring Theories for Declining Birth Rates

Ineffectiveness of Financial Incentives on Birth Rates

Correlation Between Religiosity and Birth Rates

Birth Rates and Their Role in U.S. Culture Wars

Reconciling Women's Rights with Population Stabilization Goals

Potential Impact of Technologies like Artificial Wombs

Advantages and Disadvantages of a Shrinking Global Population

Call to Action: Broadening the Conversation on Depopulation

Global Depopulation

Global depopulation describes the phenomenon where successive generations are smaller than the ones before them. It is an inevitable outcome when the world's average birth rate falls and remains below approximately two children per two adults, marking a significant departure from historical population growth patterns.

Replacement Birth Rate

This is the average number of children per two adults required to maintain a stable population size, typically cited by demographers as 2.1 to account for individuals who do not survive to adulthood. If the global average birth rate consistently falls below this threshold, it leads to depopulation.

Ideas as Renewable Resources

This concept, central to macroeconomics, posits that knowledge and discoveries are unique economic resources that are used but never used up. They can be infinitely reapplied, leading to continuous progress and improved living standards, making a larger population beneficial for accelerating innovation.

Economics of Fixed Costs

This principle highlights how the initial, unchanging costs of establishing a service, business, or infrastructure (fixed costs) can be more easily met and spread across more individuals when there is a larger population and corresponding demand. This enables the economic feasibility of specialized goods and services that would otherwise be unsustainable.

Opportunity Cost of Children

An economic framework suggesting that the value of what individuals forgo by choosing to have children (e.g., career advancement, personal freedom, financial investments) has increased over time. This rising opportunity cost is presented as a significant, multifaceted driver behind the global decline in birth rates.

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What is global depopulation?

Global depopulation is the phenomenon where each successive generation is smaller than the one before it, resulting from global birth rates falling and remaining below an average of two children per two adults.

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What is the current global average birth rate?

The current global average birth rate is 2.3 children per two adults, a figure that has been continuously falling for centuries.

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How reliable are demographic projections about future birth rates?

While predicting exact future birth rates is difficult, demographers have high confidence in the 'if-then' nature of projections: if the world's birth rate falls below two, depopulation will occur. This confidence is supported by the global convergence of low birth rates, a centuries-long falling trend, and the observation that no country where the birth rate fell below 1.9 has ever returned to 2.

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Could a subgroup with high birth rates eventually overcome global depopulation?

While mathematically possible in theory, empirical evidence suggests this is unlikely in practice because human populations are not just mathematical biology; people make decisions, cultures change, and children often leave their subgroups or adopt lower fertility rates over generations.

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Why does global depopulation matter?

Global depopulation matters because human progress, including advancements in living standards, health, and knowledge, is driven by people. Fewer people mean fewer ideas, discoveries, and innovations, potentially hindering future progress and reducing the availability of diverse goods and services.

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What are the primary reasons for declining birth rates?

The exact reasons are complex and not fully understood, with many theories (e.g., capitalism, decline of marriage, individualism, contraception, feminism, wealth, education) failing to account for the global and long-term nature of the decline. The most credible overarching theory is a rising 'opportunity cost of children,' meaning people give up more to have kids than in the past.

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Do financial incentives or social policies effectively increase birth rates?

Evidence suggests that policies offering money, subsidies, or free social services (like daycare or college) do not significantly increase the total number of children people have over a lifetime, though they might influence the timing of births.

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How do birth rates connect to the culture wars in the U.S.?

Low birth rates have become a contentious issue, often co-opted by the political right to promote national identity, traditional gender roles, or concerns about racial demographics. This has led to a rejection of the topic by the political left, creating a 'firewall' that prevents broader engagement on the issue from those who also believe in reproductive freedom and progress.

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Could artificial wombs help stabilize the global population?

While artificial wombs could significantly improve lives by eliminating the pains and risks of pregnancy, it is skeptical that they would alone raise birth rates back to a stable level. The 'cost' of making a person extends far beyond pregnancy, encompassing many years of child-rearing, which would still remain.

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Could global depopulation solve climate change?

No, depopulation is too slow to address urgent environmental challenges like climate change. The global population is projected to keep growing for decades, and changes in birth rates operate on generational timescales, which are too slow to meet the immediate need for decarbonization.

1. Prioritize Decarbonization for Climate

Do not rely on global depopulation as a solution for climate change because it is too slow, operating on generational timescales rather than the urgent yearly changes needed. Instead, focus efforts on decarbonization to address environmental challenges effectively.

2. Dads Must Share Parenting

If society desires a future with more children, dads and potential dads must significantly increase their share of parenting work, including tasks like cleaning, nighttime care, cooking, and logistical planning. This helps spread the burdens of child-rearing beyond pregnancy, making it more feasible for parents to choose larger families.

3. Improve Parenting Support

To achieve a stabilized future where people freely choose to have an average of two children, advocate for more support, flexibility, and funding for parenting. This approach ensures a fair and equitable future for both women and men without coercing choices.

4. Engage in Low Birth Rate Conversation

Participate in discussions about low birth rates from a liberal, progressive perspective to prevent illiberal forces from dominating the narrative and shaping societal responses. This ensures that concerns about reproductive freedom and women’s progress are integrated into solutions.

5. Seek Consensus on Stabilization

Recognize that if a stabilized future population (at any level) is desired over indefinite depopulation, then global birth rates must eventually return to an average of two children per two adults and stay there. Work towards building consensus on this goal.

6. Adapt to Aging Populations

Recognize that economic adjustments will be necessary to handle an aging population, as the U.S. average age has increased and is projected to continue rising. Embrace intergenerational transfers as a positive aspect of society, ensuring continued benefits of living in a world with other people.

7. Focus on Average Birth Rate

Don’t let the debate on childlessness distract from the fact that a decline in the average number of children among parents also causes depopulation. This broader perspective helps understand the true drivers of population decline.

8. Distinguish Global from Local

When discussing population issues, differentiate global depopulation from local overpopulation or nationalistic concerns, as the latter can be driven by “awful stuff” and migration can address local imbalances. Focusing on global trends avoids these problematic distractions.

9. Financial Incentives Are Insufficient

Understand that policies offering money or subsidies for children, even significant social spending or tax credits, do not substantially increase overall birth rates. Decisions about having children are deeply personal and not easily swayed by financial incentives alone.

10. Artificial Wombs Aren’t a Silver Bullet

While technologies like artificial wombs could alleviate the physical pains and risks of pregnancy, they are unlikely to significantly increase birth rates alone. The many years of costs and efforts required for child-rearing after birth remain a major factor.

11. Invite Others to Population Discussion

If you are convinced or curious about the importance of global population strategies, actively invite more people into the conversation. This helps retire outdated overpopulation tropes and build consensus for a forward-looking approach to population.

Depopulation is the inevitable consequence of low birth rates.

Dean Spears

1.9, 1.8, that doesn't feel that different from a world that has two in it. So like the United States right now is 1.6, right? And the difference between a world at 1.6 and a world at two or 2.1, you can see it in the statistics, but I don't think you would feel it if you went to the park or went to the grocery store or went to the swimming pool or jogged around the lake.

Dean Spears

Progress comes from people, meaning that we're each better off if we share the world with more other people, more other people living at the same time of us or living before us.

Dean Spears

Ideas are a special type of resource that gets used, but it doesn't get used up. Ideas can be reapplied endlessly. They're a renewable resource. And so more people means more ideas and more progress and better lives.

Dean Spears

For $3,000, would you agree to marry somebody other than the person who you married or plan on marrying? And I've never heard anyone say, yes, I would marry a different person for $3,000.

Dean Spears

Depopulation is coming fast at the level of generations, but not at the level of years.

Dean Spears
Less than 5 million people
Global population 10,000 years ago About the size of metro Atlanta.
1 billion people
Global population in 1800 Start of rapid growth.
2 billion people
Global population in 1900 Doubled from 1800.
More than 8 billion people
Current global population Quadrupled since 1900.
0.7 kids per two adults
South Korea's birth rate One of the lowest rates globally.
1.6 kids per two adults
United States' birth rate Below the replacement level.
Slightly higher than 2 kids per two adults
World average birth rate needed for population balance Demographers typically say 2.1 to account for mortality before adulthood.
2.3
Current world average birth rate Has been falling for centuries.
Around 6
World average birth rate in 1800 Estimate, as vital registration was not widespread.
Below 6, maybe 5.5
World average birth rate in 1900 Estimate.
5
World average birth rate in 1950 Estimate.
2064
Year UN projects world birth rate to reach 2 Projected year for reaching the replacement level.
2084
Year UN projects world population to peak Projected peak at 10.3 billion people, 20 years after birth rate reaches 2.
One in five
Proportion of people living in countries with birth rates below 2 by 1980 Indicates early signs of the trend.
Approximately 1
China's total fertility rate Means 1 child for every 2 adults, leading to rapid population halving per generation.
26
Number of countries where lifetime average birth rate fell below 1.9 In zero of these 26 countries has the birth rate ever gone back up to 2.
Two-thirds
Proportion of people living in countries with birth rates below 2 today Low birth rates are now the global norm.
40%
India's female labor force participation rate Low in international comparison, yet India is a below-replacement birth rate country.
9 years
Average age increase in U.S. over last 75 years Historical change in population age structure.
Another 7 years
Projected average age increase in U.S. over next 75 years Future change in population age structure.
0.2
Correlation between U.S. religiosity and number of children Correlation between agreeing religion is important in life and number of children.
1.8
Latin America's average birth rate Below replacement, despite high reported religiosity.
90%
Estimated percentage of Christians in Latin America (2014 Pew study) Indicates high religious adherence.
70%
Estimated percentage of Catholics in Latin America (2014 Pew study) Indicates high religious adherence.
$3,000
Biden-Harris child tax credit expansion Did not significantly impact birth rates.