Key Takeaways from “After the Spike: Population, Progress, and the Case for People”
On July 9th, 2025, the Aspen Economic Strategy Group hosted economists Michael Geruso and Dean Spears for a conversation on their new book, After the Spike: Population, Progress, and the Case for People. In After the Spike, Geruso and Spears examine the decline in global birth rates and consider what a drop in the global population would mean. They make a data-focused case that depopulation threatens technological and social progress and examine how we could build a society that avoids such a future.
The program featured an opening presentation from Geruso on the data behind his and Spears’ argument. Geruso first broke down current projections for the global population, noting that the most likely future is that, after a final few decades of growth, the world’s population will face exponential decline. He continued, “Let’s imagine that the world as a whole converged to a birth rate that would feel very familiar to all of us in this room. A birth rate of 1.6, 1.6 kids for every two adults. That happens to be the birth rate of the United States today. What that sort of future would mean is rapid global depopulation.” Geruso asserts that this rapid drop —“a world population that falls by two-thirds every century”— is an undesirable future for humanity. Because humanity’s progress results from the innovations, discoveries, and technologies that people create, Geruso concludes, “A populous world is a more prosperous world with better lives on average for everybody.”
The event also featured a panel discussion with Geruso, Spears, and AESG Director Melissa S. Kearney. The panel touched on topics including overpopulation, environmentalism, and solutions that might make individuals more likely to choose to have children.
Kearney kicked off the discussion with a reference to Paul Ehrlich’s book, The Population Bomb, and asked the authors to explain their focus on the risks of depopulation, given that concern over population growth, and in particular its impact on the environment, dominates conventional wisdom. “That story missed that humanity, even then, wasn’t on a path to population growth, generation after generation forever, without any sort of end,” Spears remarked. “Falling birth rates have been around for a long time. Not only is this not just a US phenomenon, but it’s a worldwide phenomenon. It’s also a phenomenon that’s been spreading over time for a long time.”
Furthermore, on the question of the relationship between population and climate change, Spears remarked, “The question we need to ask now is whether a smaller population is going to be the solution to [environmental] challenges.” He cited China’s air pollution problem as an example. “Even though there were more people, the environmental damage was lessened because people did something different: new regulation, new enforcement, turning off coal plants,” Spears said. “People making decisions resulted in less pollution. Every time we’ve made progress against our environmental challenges before, that’s been how we’ve done it.”
On how to think of population decline in the context of rapid technological advancements, Geruso argued, “Global depopulation is not going to relieve us of our duties to confront climate change because global depopulation isn’t going to start happening for several decades after we should be making progress on climate this decade in the next. And in the same way, it’s not going to interact with AI in the way that people sometimes think because what’s going to happen with AI is going to be very fast—the next year, the next decade. The population will still be growing at that time.”
The panelists also highlighted that achieving population stabilization requires individuals to want to choose to have children, and that means that we need to make it easier for people to make that choice. Kearney remarked “the book makes it clear that the answer to this is not to restrict women’s choices and opportunities. Getting society, not just men, but society, to share in more of the care burden has to be part of the response.” Geruso emphasized, “Does addressing [population decline] mean backsliding on gender equality? Very clearly the answer is no.” He continued, “We don’t think children are women’s responsibility. We think that we all benefit from getting to live in a big world and that means we should all share in the responsibility of creating the next generation.”
Watch a recording of the event here.