Introduction
Humanity is now entering an era of global depopulation: a sustained decline in global population marked by declining birth rates in a growing number of countries. Darrell Bricker and John Ibbitson in their 2019 book Empty Planet had argued that global population decline—not growth—will be the next major challenge for geopolitics and economies. Six years later, After the Spike by Dean Spears and Michael Geruso expands on this idea, offering a thought-provoking analysis of the risks depopulation will pose to human progress.
Unlike Bricker and Ibbitson, Spears and Geruso take a rigorous empirical approach, delivering a nuanced examination of global demographic trends—past, present, and future— and their implications for humanity’s future. The book challenges conventional wisdom about population growth, arguing that the world is on the brink of depopulation rather than the overpopulation crisis many fear. Spears and Geruso, both economists with extensive research backgrounds in demography and public health, present a meticulously researched case for why depopulation is likely and why stabilising the population is a preferable alternative.
This depopulation scenario is not a distant possibility—it is already happening in many countries, including China, Japan, and much of Europe.
The book is structured into four parts, each addressing a key aspect of the population debate—the historical and projected trends in population growth (Part I); the arguments against a larger population (Part II); the benefits of maintaining a stable population (Part III); and potential policy solutions to achieve stabilisation (Part IV). Through a blend of data-driven analysis, historical context, and ethical and logical reasoning, the authors make a compelling argument that societies should actively work toward population stabilisation.
The Spike and Depopulation
The central metaphor of the book is “the spike”, which refers to the rapid rise and impending decline of the global population. The authors illustrate how human population grew exponentially over the past two centuries due to declining mortality rates, particularly in childhood, but are now poised to shrink as birth rates fall below replacement levels (around 2.1 children per woman). They project that if current trends continue, the global population will peak around 10 billion in the late 21st century before entering a prolonged decline.
This depopulation scenario is not a distant possibility—it is already happening in many countries, including China, Japan, and much of Europe. The authors emphasise that once birth rates drop below replacement levels, they rarely recover, leading to a rapid population decline over time.
Ineffective Regulations
In Part II, Spears and Geruso address common arguments against population growth, particularly environmental concerns. They debunk the notion that fewer people automatically means less environmental harm, pointing out that technological and policy innovations—not population size—are the primary drivers of environmental outcomes. Historical evidence reveals that population growth alone does not drive environmental degradation. Ineffective regulations, not demographic trends, have been the primary cause of pollution, ozone depletion, and acid rains.
For example, global average exposure to particulate air pollution has decreased since 2015 despite a population increase of more than 750 million. While China’s population grew by 50 million in a decade, its air pollution decreased by half due to regulatory changes and cleaner energy adoption. Countries such as Japan and South Korea manage to maintain low air pollution levels while being densely populated, unlike India which suffers from high pollution levels.
The book discusses the misconception that famine is caused by overpopulation, arguing instead that it is primarily a political issue. Spears and Geruso conclude by addressing the fears surrounding bringing new lives into the world, emphasising that life today is worth living despite imperfections.
When fewer workers support aging populations, innovation slows, and GDP growth falters, with fixed costs straining businesses and limiting market viability.
They also tackle the ethical and social implications of depopulation, such as gender inequality and reproductive freedom. They argue that stabilisation does not require coercive policies or a reversal of women’s rights. Instead, it can be achieved through societal support for parenting, such as better childcare policies, workplace flexibility, and shared domestic responsibilities.
Benefits of a Stable Population
In Part III, the authors argue that human progress—scientific advancement, economic growth, and cultural innovation—has historically flourished in larger and interconnected societies. They warn that population decline could trigger economic stagnation. When fewer workers support ageing populations, innovation slows, and gross domestic production (GDP) growth falters, with fixed costs straining businesses and limiting market viability. Larger populations, they explain, sustain diverse industries—from restaurants to healthcare—by providing a robust consumer base, while also fostering greater innovation through expanded markets.
Beyond economics, the authors caution that a shrinking talent pool could stifle innovations in technology and medicine, leading to a scientific decline. Smaller societies may also lack the resilience to withstand crises such as pandemics or climate disasters.
Challenging “lifeboat ethics”, which frames population reduction as a solution to scarcity, Spears and Geruso present data showing rising global living standards amid population growth, which has been driven by advances in agriculture, medicine, and governance. They reject the notion that only quality of life matters, asserting that both quantity and quality are essential for sustaining humanity’s trajectory of development.
Policy Solutions for Stabilisation
In the final section, the authors examine how societies can achieve population stabilisation without coercive measures, condemning top-down approaches like China’s one-child policy as both unethical and ineffective. Instead, they argue that truly sustainable population stabilisation depends on protecting women’s rights and reproductive freedom, while also creating economic and social conditions that make parenting practical and affordable.
To encourage balanced birth rates, they propose policies that reduce barriers to parenthood, including financial incentives such as child allowances and tax credits, workplace reforms such as paid parental leave and flexible schedules, and broader cultural shifts to elevate the status of care-giving and distribute its burden more equitably. Importantly, they frame stabilisation as a societal responsibility—requiring collaboration among governments, employers, and communities—to create conditions where individuals can freely choose parenthood without compromising their economic stability or personal aspirations.
Strengths and Unresolved Issues
Grounded in rigorous demographic and economic research, the key strength of this book is its data-driven analysis of population trends, using historical evidence, cross-country comparisons, and future projections to build its case. Spears and Geruso maintain a balanced perspective, thoughtfully considering both the benefits and challenges of population changes. They avoid sensationalism, acknowledging environmental pressures but showing how these issues can be addressed without resorting to depopulation.
Despite the complex subject matter, the writing remains engaging and accessible, skilfully weaving in personal narratives and vivid case studies to give a human dimension to the statistical analysis.
The authors establish clear ethical boundaries, unequivocally rejecting coercive population controls and emphasising reproductive autonomy, framing their vision of stabilisation through empowerment rather than restriction. Despite the complex subject matter, their writing remains engaging and accessible, skilfully weaving in personal narratives (like the family story of one of the authors, Micheal Geruso) and vivid case studies (such as the nurses in Uttar Pradesh) to give a human dimension to the statistical analysis.
Despite its remarkable strengths, After the Spike leaves a few critical gaps unresolved. It fails to substantively engage with alternative frameworks like Vegard Skirbekk’s Decline and Prosper (2022) and Andrew J. Scott’s The Economics of Longevity (2023), which argue that adapting work for ageing societies may be more viable than reversing decline. The book also overlooks other frameworks such as the “silver dividend” (leveraging older workers’ experience for sustainable economies) and “care poverty” (unmet care needs among elderly/disabled populations) (Nair and Goli 2025). In particular, the concept of care poverty, emphasises the importance of population support ratio for non-economic needs of older people.
The authors are optimistic about technology, and this is persuasive when it comes to issues like air pollution. Julian Simon's famous bet with Paul Ehrlich proved that resource prices can decline due to innovation and technological progress. By 1990, the real prices of Ehrlich’s selected commodities had dropped by over 50%, illustrating how advancements in technology and resource management increase abundance and reduce costs (Birdsall et al. 2001). The text contends that human ingenuity will continue to overcome resource scarcity through innovation. However, they tend to overlook more difficult challenges such as biodiversity loss and water scarcity. They also do not fully address the political challenges of implementing their proposals, as the limited success of pro-natalist policies in countries like South Korea and Japan show.
Debates on gender equity and fertility rates—including those by Spears and Geruso—frequently neglect critical insights from feminist scholarship and movements. The authors’ claim that global examples show no consistent correlation between lower birth rates and smaller gender pay gaps among Organisation for Economic Co-operation and Development (OECD) countries appears simplistic. Such assertions require stronger evidence from diverse cultural contexts.
The core issue is that boosting birth rates requires true gender equality, especially in patriarchal Asian societies. Existing inequalities spark feminist resistance to pro-natalist policies, which are seen as exploiting women without fixing systemic problems.
While it would be unfair to claim that the authors have not positioned gender equity as a foundational pillar for achieving population stabilization, the evidence and arguments presented in the book may still fall short of persuading feminist critics opposed to the resurgence of government-led pronatalist policies worldwide. Several Asian countries that experienced fertility transitions later than Western Europe - including South Korea, Singapore, and parts of India - now show even lower fertility rates than European nations. This trend stems primarily from severe gender inequality and motherhood penalties (the economic and career disadvantages women face due to traditional gender roles).
Growing numbers of women are opting out of marriage altogether to avoid discrimination within marital relationships. Unlike some European societies where single parenthood is acceptable, non-marital childbearing remains culturally stigmatized in many non-European socieities, severely limiting women's reproductive choices. Many highly educated women fear having children because they lack confidence that men will share domestic and childcare duties equitably. These concerns reflect deeper anxieties about losing personal autonomy, self-worth, and opportunities for self-fulfilment within traditionally unequal marriages.
While low fertility in East Asia and developed countries results largely from work-life balance challenges and evolving social norms, India's situation is different. Here, economic factors - particularly the high costs of education, healthcare, and housing - remain the dominant constraint on family size. Nevertheless, in urban India's more affluent households, social factors are becoming increasingly influential, mirroring patterns seen in wealthier nations. Given this context, Spears and Geruso could have explored why efforts to create parenting friendly environments—which are crucial for maintaining birth rates—often fall short. Many programmes do not consider changing gender expectations or uprooting deep-seated discriminations (not just economic factors) that vary across cultures.
The core issue is that boosting birth rates requires true gender equality, especially in patriarchal Asian societies. Existing inequalities spark feminist resistance to pro-natalist policies, which are seen as exploiting women without fixing systemic problems. Modern feminism focuses more on personal fulfilment (self-actualisation) than just economic needs—a tension After the Spike has not delved into deeply. Without addressing how pro-natalism clashes with local patriarchies or redistributing care work, its solutions miss the mark in the regions needing them the most.
Conclusions
After the Spike is a timely and important contribution to the discourse on population dynamics, although not completely new to scholars in the demographic community (Birdsall et al. 2001). The book revives the anti-natalist-pro-natalist debate, challenging the “fewer people equals better planet” argument. Instead, Spears and Geruso propose a balanced approach focused on well-being, equity, and sustainable progress. Their call for a population stabilisation—achieved through empowerment, not coercion—is both visionary and pragmatic. By focusing on human flourishing rather than mere survival, the authors encourage readers to imagine a future where parenting is fulfilling, progress benefits everyone, and depopulation is not seen as unavoidable.
Ultimately, After the Spike is not just about demography, ecology and economics—it is about the kind of future we want to build.
The book is essential reading for academia, research communities, policymakers, environmentalists, and anyone else interested in the future of humanity. The authors invite readers to participate in a broader discussion about the implications of depopulation and the need for supportive measures for families. It reframes the population debate away from fear and scarcity towards opportunity and collective action. While the challenges of stabilisation are significant, the authors are convincing in their argument that the alternative—a depopulated world—poses far greater risks to the prosperity and resilience of our species.
Ultimately, After the Spike is not just about demography, ecology and economics—it is about the kind of future we want to build. As Spears and Geruso remind us, the choices we make today will shape the lives of generations to come. Ultimately, the central message is that the choice is not between people or the planet—it is about creating a world where both can thrive.
Srinivas Goli is an Associate Professor of Demography at the International Institute for Population Sciences (IIPS), Mumbai.
