1 While there is now a consensus on announcing a global population decline, projections differ considerably. For United Nations (UN) experts, who are still leading the debate, the most likely hypothesis is that the peak will be reached shortly after 2100, with a global population of 10.9 billion compared to nearly 8 billion today. But there is a wide range of possibilities among all the projections, and the peak oscillates between 9.4 and 12.7 billion. This is due to variations in estimates about changes in fertility rates on the one hand, and mortality on the other. Other voices are rising, meanwhile, to announce a major crisis induced by global warming, that will result in the collapse of the population from 2050. Although demographer Henri Leridon considers such a hypothesis implausible, he thinks the rapid fertility drop lends credibility to the UN’s low-variant hypothesis. His colleague Hervé Le Bras follows the same line of thought. Picking out a number of biases in the UN’s main scenario, Le Bras argues that the experts tend to underestimate the decline in fertility and overestimate the rise in life expectancy. He believes the peak will be reached between 2060 and 2075.
2 Le Bras also cautions against the temptation to consider the world’s population as anything other than a “conceptual construct.” This echoes an analysis conducted seventy years earlier by demographer Alfred Sauvy, who protested against the catastrophic prognoses formulated at the time on the risks of a demographic explosion and contested the idea of imposing birth control. Sauvy was already affirming that the main factor behind fertility rates is the development of education and health care. History proved him right.
A wide range of hypotheses
3 Since the 1960s, the scenarios elaborated by UN experts have been derived from what is deemed to be a proven method: The “cohort-component” method, based on analysis of levels of fertility and mortality, by age and sex. Aggregating the projections made for each country, the UN Population Division publishes its global projections every two years. In Population & Societies, the journal of the Institut national d’études démographiques (INED) (National Institute for Demographic Studies), Henri Leridon breaks down the main hypotheses resulting from these projections and questions the legitimacy of the most pessimistic scenarios rolled out today.
4 The UN presents a central hypothesis called the “medium variant,” branching off above or below into several variants, that are deemed less likely. The medium variant projects an additional gain of 3.2 billion people between 2019 and 2100, with the global population then leveling out at 10.9 billion, before beginning to drop. But “the diversity of past trends” in fertility rates introduces a vast potential margin of error. In 2100, the world population may reach only 9.4 billion, or, by contrast, peak at 12.7 billion. Demographers also engage in purely theoretical calculations: If fertility is arbitrarily lowered by 0.5 children per woman compared to the medium variant, the population in 2100 is reduced to 7.3 billion—that is, less than today; whereas if it is increased by 0.5, the peak reached in 2100 is 15.6 billion.
5 Since the 1950s, notes Henri Leridon, the population curve has stayed close to the “medium-variant” projections. Is it conceivable that this might change in the future? He speculates. The UN assumes that fertility rates will keep dropping, as they have over the past decades, except for a slight increase projected in Europe and North America. For sub-Saharan Africa, the medium variant more than halves current fertility rates: from 4.72 children per woman to 2.16 in 2100. Alternatively, the UN experts engage in further conjecture, theorizing an immediate and general transition to 2.1 children per woman (replacement level fertility). This would imply an increase in countries where the rate is lower, and a decrease elsewhere. The result is close to the medium variant.
6 Henri Leridon points out that the drop in fertility may be greater than anticipated by UN experts and that the reality is now approaching the low variant. He then examines the most pessimistic scenarios, put forward by “collapsologist” authors who conjure up the possibility of a “sharp increase in mortality.” The UN’s medium variant projects a continuing decline in mortality—like fertility—due to rising life expectancy. But it also considers the possibility that the mortality rate will level out, which would limit the world population to 8.92 billion in 2100. Collapsologist theories are based on the idea of the potentially catastrophic impact of climate change on agricultural production and access to water. The model used by the authors of the Club of Rome report, drawn up in 1972, is aired anew here, in light of a projected population collapse starting in 2050. Henri Leridon considers such a prospect unlikely. If the UN’s low-variant projection is likely to come true, it “is due to a rapid fertility decline, and not an increase in mortality.”
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The questionable ecumenism of the United Nations
8 The methodology followed by UN experts is not free from bias, explains Hervé Le Bras in Politique étrangère. “The United Nations wants to create a peaceful image of the world in 2100, because that is part of its mission,” he writes. The organization therefore makes its projections converge in 2100 “on values of between 1.7 and 2.35 children per woman, with three exceptions: Niger (2.5) [. . .], Zambia (2.45), and Singapore (1.45).” For the demographer, the convergence results merely from circular reasoning, begging the question of whether this is a sign of “questionable ecumenism.” Without providing the slightest explanation, the UN raises the fertility of countries like Portugal, Poland, and South Korea. Just as unaccountably, fertility in France is supposed to stabilize at 1.94 in 2100, whereas it has, in fact, already fallen to 1.87. Moreover, the United Nations “has assumed that decreases in mortality will continue in all countries.” Life expectancy is predicted to reach 82.5 years for the whole world in 2100, compared to 71 years in 2015. In the United States, it would reach 90 years of age—despite the fact that it has actually been decreasing for several years.
9 To establish credible projections, Hervé Le Bras therefore considers it wiser to resort to a different methodology: Quite simply, to follow the changes in the growth rate of the global population, extending them into the future. In the decades following the Second World War, the growth rate rose steadily: 1.75 percent per year in 1955, 1.9 percent in 1960, 2.1 percent in 1970. But that was the maximum; and two years later, when the famous report to the Club of Rome appeared, “peak population growth had already been passed.” Since then, it has “slowly declined” and now stands at 1.1 percent per year. However, the extension of the trend “leads to a growth rate of zero between 2060 and 2075, much earlier than in the United Nations’ projections” in their medium variant (where zero is reached a little after 2100).
10 Hervé le Bras also cautions against the temptation to consider the global population as “a homogeneous reality.” In reality, it is a “conceptual construct.” The main focus of attention should in fact be placed on “two problematic parts of the world”: tropical Africa and the part of West Asia formed by Pakistan, Afghanistan, and Iraq. Le Bras demonstrates that there is a correlation between high population growth and political unrest.
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A false problem?
12 The future of the global population has been hotly debated ever since the time of Malthus. More recently, in 1948–1950, William Vogt made a splash with his best-selling book The Road to Survival. In an article published in the Population journal in 1949, demographer Alfred Sauvy seized the chance to express his skepticism concerning ideas that he found simplistic. It is interesting to read this text again today, because in many respects, it has lost none of its zest and remains just as topical.
13 Vogt’s thesis resembles that of Malthus: The growth of the global population will outpace that of subsistence resources, so measures must be taken to keep it in check. While Malthus advocated abstinence, Vogt pressed for birth control to be imposed in poor countries. Countries that refused would be deprived of development aid. Sauvy affirms that with this line of argument, Vogt aligns himself with Malthus, who “considered it pointless to improve the lot of the working classes.” For the demographer, such a position stems from “rigid conservatism,” a central element of which is the “negation of technical progress.” He berates the “pessimists” whose “gloomy prognoses do not take scientific and technical progress into account.”
14 Sauvy takes this opportunity to call the very concept of global population into question. The world is not a homogeneous entity. National borders “compartmentalize” it. This phenomenon became increasingly pronounced in the aftermath of the First World War, with the creation of the League of Nations, predecessor to the UN. “If we can say that a French population exists, or a Japanese population, or any population, it is only because there is a linguistic, ethnic, or political unity behind it and because, within the borders that surround these populations, human migration and trading of goods are completely free.” The demographic situation varies greatly according to the countries and regions of the planet: changes in populations must therefore be considered country by country. And, in a world where colonial empires are gradually giving way to nationalism, it is futile to seek to impose any demographic policy from the outside. The people who dream of birth control belong to “the ruling classes” of rich countries: “The fear of the multiplication of others thereby leads to [. . .] an upsurge of Malthusianism in populations already debilitated by demographic aging.” The desire to control births springs from an illusion. To seek to impose such a measure would not help—at best, it would play an “accessory” role. Dropping fertility rates are, in fact, essentially down to improvements in education and health care: “As soon as education and health care develop, the cost of bringing up a person rises, and the intensity of the effort required causes a decline in reproduction.” For developed countries, “the danger that generations do not ensure their own replacement is higher than that of excessive multiplication.” That is why, “to be of greatest use, research should address differential fertility.” Seventy years after this text was published, its premonitory character jumps right off the page.
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Translator: Sophie Cherel, Editor: Suzy Bott, Senior editor: Mark Mellor