‘Depopulation would mean fewer people contributing to advancement of knowledge’

Trends show that in a few decades, global population will begin to shrink. Once depopulation starts, no one knows how to stop it in a sustained way, write Dean Spears and Michael Geruso, associate professors of economics, University of Texas at Austin, US, in their recent book, After the Spike. The authors, who are also economic demographers, argue that population decline will be detrimental to global progress and that a smaller population would not necessarily be better for the environment. In an interview with Aditya Misra, they say that the time to talk about depopulation is now because the search for a solution could take decades. Excerpts:

What are the consequences of depopulation—the worst-case scenarios—that the world needs to worry about or be prepared for?

A future with fewer people will be a future with slower improvements in some areas and stalled progress in others. Over the long run, larger populations—not only national populations, but the global population—make each of us better off. That’s one argument (though not the only one) that we make in detail in our book After the Spike: Population, Progress, and the Case for People. Living in a big world with many other people makes each of us better off. As we wrote recently in The New York Times: “Whenever people need and want things, they make it more likely that you will get what you need and want. That’s true if what you want is good public transportation (because a network of trains and buses can’t operate without enough riders), or green energy infrastructure built on the work of scientists and engineers across generations and borders, or a vaccine for a novel virus, or a cure for a rare disease that only the niche medical specialisation of a big world could produce.”

The past two centuries were a revolution in better living standards as our population climbed. We should not be complacent about retreating to a smaller world.

You write that when depopulation happens, it would not spontaneously halt at a smaller point. Why would it not? Would countries not take steps to check depopulation if it becomes a problem? Why should it be a concern now?

There is no reason to expect an automatic reversal, nor is any playbook sure to halt global depopulation once it starts.

Depopulation, which is when the population shrinks generation by generation, is the unavoidable consequence of there being fewer than two children in the next generation to replace two adults in the last generation. Two-thirds of people now live in a country where the birth rate is below the two-births-per-two-adults average that would stabilise the population. Even after shrinking for a decade or a century, as long as the global average birth rate held below two, the world would go on shrinking.

Will the birth rate fall below two for the world as a whole? We do not have a crystal ball, but in the “National Family Health Survey (NFHS-5) 2019-2021”, young women in Uttar Pradesh told surveyors that they want an average of 1.9 children. A future where women in Uttar Pradesh are having 1.9 children, on average, is probably a future where people elsewhere are having even fewer. No country has discovered a policy response that substantially raises birth rates in a sustained way. Japan has been shrinking for 15 years. Italy has been shrinking for a decade. China begun shrinking more recently. Governments around the world have wanted to reverse low birth rates and have tried to do so. And yet, in none of these places, have lifelong birth rates risen back above the replacement level after they have fallen substantially below it. To the extent that population decline has slowed or reversed in some places, it has been due to immigration. But immigration offers no solution to global population decline. The Earth is a closed system, only births and deaths determine population growth. Immigration plays no role.

Global depopulation will not begin for several decades. One reason to pay attention now is that no one—not social scientists, not elected leaders—yet knows how to halt the coming decline and the search for solutions may take decades.

The Prologue says there is a need to talk about depopulation because “some of the people talking about low birth rates are diverting attention from real challenges and solutions. They are talking about depopulation to suit their agendas—of inequality, nationalism, exclusion, or control”. Could you elaborate with examples?

The politics of this play out a bit differently in the US (where access to reproductive health care is under threat as a prominent policy issue) and in India, where abortion has been legal since 1971. But one example from the US is Matt Schlapp of the Conservative Political Action Conference saying, “If you say there is a population problem in a country, but you are killing millions of your own people through legalized abortion every year, if that were to be reduced, some of that problem is solved.” Global depopulation will bring big changes in an unprecedented future. That is important enough that we should not leave the conversation on to just a few people, or to one side of the political spectrum—and we certainly should not let those who would seek to dictate other people’s family lives be the only voices we hear.

The book says that stabilisation is better than depopulation. But it does not give an estimate of the population at which the world should stabilise. Unless that number is known, isn’t the problem we are trying to solve largely theoretical?

Asking what the right number of people on the planet is a bit like asking what is the right number of teachers, or doctors, or engineers in some city. There’s not some single critical number that we could all agree on, but we should all agree that some things will be very hard to accomplish without enough such people.

It would be beyond the reach of today’s social science or climate science or any other science to defend some specific population size as ideal. The stabilisation that we argue for is only this: avoiding depopulation without end. And unless birth rates rise to about two after they have fallen low, depopulation is the inevitable consequence.

Population growth has been a problem in many countries, and so it would seem counterintuitive to say that depopulation is not a solution, at least to some extent and in the shorter term, for the environment. Would you agree?

For the past two centuries, progress has unfolded as the global population expanded. The data tell us that lives are better now than lives were in the past in terms of health, education, freedom, longevity, and economic security. Children in India grow taller than even a few decades ago and are much more likely to survive the start of life–like elsewhere in the world That is true even though there are now billions more lives around. Fears of a depleted, overpopulated future are out of date.

For a long time, India was at the centre of fears about “overpopulation.” Today, lives in India are richer than ever. They are longer than ever. They are healthier than ever. So “overpopulation” did not bring doom to India—and we have plenty to say in our book about why not.

Yes, there are lives that we all should work to improve. But the chances for a good life for a child are at least as high now as they have ever been, in all of human history. Ever more parents can expect good lives for their children. It is true in Texas, it is truer than ever before in India, and it is true averaging over the whole world.

What future do you see for India in this depopulation scenario and how will it impact the world?

One sixth of all people on the planet live in India. So, whatever happens in India will be undeniably important for the world as a whole.

It is hard to predict, in a shrinking world, the path that any one country will take. Even if we knew what Indian (or American or Chilean) political attitudes towards immigration would be in the coming decades, focusing on national outcomes is too narrow: The biggest economic benefits of larger populations—overcoming fixed costs and generating endlessly reusable new ideas—do not stop at national borders. When the world population begins to decline, it will mean smaller global markets thirsty for innovation and progress, and fewer people in India (and Brazil, China, and elsewhere) will be contributing to the advancement of knowledge.

This interview was originally published in the October 16-31, 2025 print edition of Down To Earth