The Indicator from Planet Money: We're Nearing 'Peak Population.' These Economists Are Worried

Release Date: July 1, 2025

In this insightful episode of The Indicator from Planet Money, host Adrian Matthew delves into the pressing issue of global population trends with esteemed economists Dean Spears and Mike Gerusso from the University of Texas at Austin. Together, they explore the concept of "peak population," the potential consequences of a shrinking global population, and the interconnectedness of population dynamics with economic progress and environmental challenges.

Understanding Population Growth and Decline

The episode kicks off with Dean Spears highlighting a paradoxical trend:

"Over the past century, the world's population has exploded, going from around 2 billion people to 8 billion people today. Even as the Earth's population has boomed, the average fertility rate has declined." (00:11)

Spears explains that while the global population has surged, the average number of children per woman has been decreasing, a phenomenon observed across continents—from North America to Asia. This decline in fertility rates poses a long-term risk of depopulation, where the global population could eventually shrink after peaking.

Mike Gerusso adds nuance to the discussion:

"Depopulation wouldn't require people having smaller families than they do today. Family sizes like today's would be enough to cause depopulation." (03:31)

Their collaborative research projects a peak population of approximately 10 billion by 2080, followed by a gradual decline over the next three centuries down to about 22 billion. This projection underscores the fragility of current population trends and the looming challenges they present.

The Impact of Depopulation on Economic Progress

Spears and Gerusso argue that a declining population could impede economic and societal advancements. Gerusso emphasizes:

"Depopulation would mean less progress on all the things that we all care about. The world's become a safer, richer place over the same narrow span of human history when the population's been booming. And that's not a coincidence." (04:21)

The economists identify two key economic concepts to support their case for a larger population:

1. Idea Generation: Building on Paul Romer's Nobel Prize-winning work, they assert that a higher population fosters innovation and economic growth. Every individual contributes to the pool of ideas, driving advancements not just in high-tech fields but also in everyday technologies and organizational methods.

   "Innovation doesn't just mean high tech. So, yes, like tailored gene therapies come from human innovation, but so does the technology of how to organize a construction crew or a kindergarten classroom." (05:00)

2. Fixed Costs: Many societal advancements involve high initial investments with minimal incremental costs for additional beneficiaries. Examples include vaccine development and public infrastructure. A larger population ensures a critical mass that justifies these fixed costs, enabling widespread benefits.

   "We have a vaccine for RSV. We have a vaccine for chickenpox, vaccine for Covid. ... there's no vaccine for sealpox because only a few people a year get sealpox." (06:29)

Gerusso further illustrates how essential a sizable population is for maintaining and advancing these public goods.

The Relationship Between Population and Climate Change

Addressing potential counterarguments, Spears and Gerusso tackle the notion that a smaller population might benefit the planet. Gerusso counters:

"Think about climate change... humanity's numbers are probably going to keep growing for the next 50 years or so. ... The only path to successfully addressing climate change and other issues is to take them head on. To reduce per capita pollution, to reduce per capita greenhouse gas emissions." (07:25)

Spears clarifies that population decline should be considered separately from environmental challenges:

"Population decline, climate change, these should be separate issues." (07:52)

Their stance emphasizes that mitigating climate change relies more on reducing individual carbon footprints and advancing sustainable technologies rather than merely decreasing the number of people on the planet.

Possible Solutions and Future Prospects

When prompted about solutions to the declining fertility rates, the economists admit uncertainty:

"Perhaps the surprising answer is that we don't think anybody has a solution to this problem." (08:26)

However, they suggest that societal shifts are necessary to encourage balanced family sizes. Spears envisions a future where:

"People choose to have an average of two kids per two adults. ... parents get more of the support that they need." (08:45)

This involves fostering a society where child-rearing is a shared responsibility, and extensive support systems are in place to make raising children more feasible and appealing without reverting to outdated gender roles.

Conclusion

Spears and Gerusso's exploration of "peak population" underscores the intricate balance between population dynamics, economic growth, and environmental sustainability. Their discussion sheds light on the often-overlooked implications of declining fertility rates and the urgent need for societal adaptations to maintain a prosperous and innovative global community.

As the world approaches this critical juncture, understanding and addressing the factors influencing population trends will be paramount in shaping a sustainable and thriving future for humanity.

For a deeper dive into these topics, Dean Spears and Mike Gerusso's forthcoming book, "After the Spike: Population Progress and the Case for People," is set to release on July 8th.