Optimum Population

Lindsey Grant

Overcoming ‘Growthmania’

The very idea of defining an “optimum population” challenges centuries of economic and political assumptions that growth is by definition a good thing. So be it. The challenge of overcoming that assumption is at least as important as any optimum population number we may calculate.

How ‘Growthmania’ Began

Before the 1300s, unlimited growth scarcely figured in human thinking. Then came the Renaissance, the age of exploration, the agricultural and industrial revolutions, and a worldwide scientific enterprise that is still accelerating—a period of enrichment and growth without parallel in human history. Its success led to a widespread conviction that growth is natural, desirable, and forever benign. In important ways, the West is still caught in that Age of Exuberance—in a state of “growthmania”—and we are busily communicating it to the Eastern and Southern hemispheres.

Growthmania is a formidable belief system. Curiously, it originated in a sudden, brutal population reduction: the fourteenth-century Black Death, the sharpest population collapse in human history. The Black Death readjusted the ratio of people to land, leaving peasants who survived with more farm-land and wealth. New wealth flowed into depopulated cities. The institutional constraints of feudalism were swept away, replaced by the first stirrings of what we now know as capitalism.1 The subsequent age of exploration further improved the ratio of land to people by opening the New World, more than quadrupling the arable land available to Europeans.2

In the twentieth century, modern medicine and public health programs lowered mortality in the poorer countries.

Modern agriculture fed the rising numbers. But too little was done too late to lower fertility. That created a fundamental demographic imbalance. The resulting population growth dwarfed all previous human experience. World population quadrupled in one century, a change so astonishing that it has altered—or should have altered—our assumptions regarding humanity’s connection with the rest of the planet.

Capitalism favors the entrepreneur, the business adventurer. It serves the successful, and so do its theoreticians. Today, conventional economics is grounded in the expectation of endless growth: economic growth for greater profits and population growth for more markets and cheap labor. Sadly, thinking in terms of economic growth per capita would be more reasonable.

Mighty Engine, No Brakes

Are we plunging toward collapse because of our very success? Philosophers since John Stuart Mill have warned against the illusion of perpetual growth. Endlessly expanding numbers cannot enjoy endlessly expanding consumption. Post-Keynesian economists ignore the fact that material growth must at some point become a logical impossibility on a finite planet. When?

John Maynard Keynes is something of a demigod to conventional economists. Yet he was never as wedded to growth-mania as many of his followers. He raised serious questions: Can growth go on indefinitely? Would it be desirable?3 Is market capitalism motivated by greed a sound moral basis for society? Two hundred years ago, Thomas Malthus worried (perhaps prematurely) about how many people the earth could support, but he did not ask the next question: What will increasing human numbers do to the planet? George Perkins Marsh in 1864 was the first to address that question systematically.4 Science has been describing the impacts ever since. In 1992, the presidents of the premier scientific bodies of the United States and Great Britain adopted a joint statement, later adopted by the world’s major national scientific societies, that read: “If current predictions of population growth prove accurate and patterns of human activity on the planet remain unchanged, science and technology may not be able to prevent either irreversible degradation of the environment or continued poverty for much of the world.”5 A nonconformist macroeconomist, Herman Daly, makes a point his colleagues ignore: The economy is not independent; it is a subset of the environment. The biosphere is not just a sink for the waste products of economic activity. It is the matrix that sustains life, including human life, and we must ask whether human economic activity is degrading it.

Population growth is not necessary for well-being. The examples of Japan and Western Europe make that case, as did a Brookings Institution study of U.S. metropolitan areas that soundly rejected “the idea that achieving income growth in a metropolitan area requires population growth.”6 Other studies have shown that residents of stable cities are likely to be better off than those in rapidly growing ones, both economically and in terms of quality of life. Pittsburgh, long the epitome of the “rust belt,” ranks at or near the top on both scales, despite two generations of population decline—and despite its wretched weather.

A growing literature challenges the fixation on growth. It charges that the benefits of growth have gone to the entrepreneurs rather than to the mass of working people and that this growth has run down the natural capital of the earth in ways that do not appear in GNP statistics.7 Mainstream economics has ignored that literature. In the pursuit of growth, it has brushed aside every doubt raised by others. The enthusiasm for population growth is a particularly American phenomenon, but it is hardly universal. Elsewhere in this issue of Free Inquiry, Alan Kuper and Edward Tabash describe questions about U.S. population growth raised by President Nixon and the Rockefeller Commission and further explore the ongoing debate as to the wisdom of growth.

Growth must stop. The question is, when and where will it stop?

The Measurement of Optimum Population

What do we mean by “optimum population?” Optimum population is not maximum population. It is not simply sustainable population, which does not address the question “Sustainable at what consumption level?” In theory, an optimum population level should be one at which all could live a comfortable life without degrading the capacity of the environment to support that style of life in the future. It is the antithesis of current economic goals, but it should be congenial with the economic aspirations of all but the greedy. And it is a vision of a future without the threat of collapse.

Putting numbers on optimum population is more hunch than science. What yardsticks can show whether further population growth is bad—whether smaller numbers would serve humanity better? I will identify a few examples.8

Food. The world has run through the windfalls provided successively by the Black Death and the opening of the New World. Much smaller populations with more land per capita could provide a cushion against the threats to food production. Instead, population growth outstrips growth in food production. Arable land per capita in the United States and in the less developed countries has declined by one-third since 1970, and in Europe by one-fifth, in just thirty years. Fertilizers and pesticides offer diminishing returns; the world now uses about six times as much commercial fertilizer as it did in 1950 and twenty-five times as much chemical pesticide. Each new pesticide is matched by evolving pesticide resistance in pests; we run in a squirrel cage. Human activities inject nitrogen compounds, potassium, phosphates, and sulfates into the environment far faster than natural processes, with consequences we are barely beginning to understand. Much of the world is well into a water crisis, but monocultures and high-yielding “green revolution” crops demand more water and also more pesticides. Modern agriculture depends on fossil-fuel products to run machines and to provide feedstock for fertilizer, but fossil fuel shortages loom (see below). Finally, climate change threatens crop yields, especially in poorer countries.

Yet world food production could be sustained at roughly half its present level with a judicious combination of organic manures and chemical fertilizers. (U.S. corn yields were about 40 percent of current yields before modern reliance on commercial fertilizer and pesticides.) This would demand widespread changes in how we manage livestock and indeed human manures, but that in itself would solve some serious pollution problems. Very roughly, half of current agricultural production would support half the present population, and it would be a much more beneficent system.

Health. The American Chemical Society’s worldwide registry of chemicals lists four times as many chemicals as it did in 1980. Some are known to cause health problems including cancer, endocrine disruption, immune-system suppression, infertility, and learning disabilities in children. Few have been test-ed for their impact on health or the environment. Meanwhile, urban populations in the less-developed world shot up from three hundred million in 1950 to two billion in 2000, propelled largely by desperate peasants moving to cities to stay alive. Water supplies, sewage services, and electric supplies have lagged behind. Growing urban populations reuse raw sewage with disastrous health effects. It is remarkable that crowded third-world slums have not generated more epidemics. With the public-health measures that kicked off the population explosion now in disarray, rising mortality may forestall the urban population’s projected growth to four billion by 2030.

The Microbial World. The proliferation of chemicals may soon endanger micro-organisms we depend on. For example, soil microbes have so far converted nitrogen fertilizers back into inert molecular nitrogen fast enough to keep us from swamping the earth in nitrogen compounds. But we don’t know how much of a chemical load the microbes can tolerate. A much smaller human population would greatly reduce the introduction of chemicals into an environment that humans are changing but do not fully understand.

Fisheries. Worldwide marine fish production rose from twenty to over seventy million tons between 1950 and the late 1980s then stalled. Aquaculture (fish farming) enjoyed soaring growth. But aquaculture pollutes water, competes with livestock for feed, and concentrates harmful chemicals that humans put into the environment. (The Environmental Protection Agency recommends eating one serving or less of farmed salmon per month.) Humans and fish would be better off if our demand for fish were closer to the 1950 level.

The Energy Transition. Fossil energy is a profound disturbance to the ecosystem. It moves carbon and lesser amounts of other elements from the lithosphere into the biosphere and atmosphere at rates greater than all natural processes. We worry about terrorists constricting our petroleum supplies, but the supplies will decline soon anyway—an environmental boon but an economic disaster, unless we have prepared for it. U.S. crude oil and natural gas production peaked more than thirty years ago. Domestic crude oil production has fallen 40 percent and gas production 13 percent from their historic highs. World petroleum production will begin a similar decline, probably in twenty years or less. Competition for gas and oil will intensify; prices will rise sharply. There is no assurance that the United States, by far the largest gas and oil importer, will find willing exporters. As trade deficits mount—and given the prospect that in a generation or two, Americans may be eating all their grain rather than enjoying an exportable grain surplus, we may have little to exchange for others’ crude oil and gas. Coal is more abundant, but it is a dirty fuel and a prolific source of carbon dioxide, which drives climate warming. Growth apologists look to oil sands or ocean clathrates or biomass, but all of them have severe limits.

The world, in other words, is headed for an energy transition, probably toward a mix of coal, nuclear, and more benign renewable power. Rising costs and resource dislocations will threaten the world’s economies. Smaller populations would make this transition, too, easier, but demographics move slowly.

Climate. Energy production generates climate change, which is beginning to have a huge impact on human welfare. The Intergovernmental Panel on Climate Change (IPCC) in 1995 estimated that it would take an immediate reduction in carbon emissions to 30 to 50 percent of present levels to hold the human impact on climate at its present levels. In the face of that calculation, the modest reductions of the Kyoto protocols are largely symbolic.

We must address population size to come close to the 30 to 50 percent goal. With populations at 1950 levels, we would be close to or within the IPCC’s 30 to 50 percent target, even without reducing per-capita emissions.9

Technology, the Headstrong Servant. Modern Americans regard technology as a deus ex machina to solve our problems, but it has its limits. Consider two examples: First, when the Clean Air Act took effect in 1972, technical fixes caused immediate reductions in some principal pollutants. Eventually the most viable fixes had all been applied; in recent years overall air pollution has started rising again. Not just technology, but lower numbers and lower demand are central to reducing pollution. Second, consider the link between technology and job creation. Conventional economists expect economic growth to create jobs for growing populations. But technology has driven productivity up—more work can be done by fewer people, especially as employers add automation—and so economic growth need not necessarily spark job growth. As the current “jobless recovery” demonstrates, the solution for unemploy-ment is fewer workers competing for jobs. Proponents of rising immigration, take note.

Social and Economic Equity. China and India explicitly seek to raise their per-capita incomes to levels typical of the industrial world. Most poor nations seek to follow them. To support all humans at first-world consumption levels without increasing gross world-economic activity and without putting new strains on the world’s environment, world population would have to be little more than one billion, a most unlikely figure.

Nonlinearities. My analysis so far has been linear, assuming that so much more of a given input produces a comparable change in output. But nature is seldom linear. Climate studies reveal numerous nonlinearities—feedback loops that may disproportionately intensify prospective changes. Examples include alterations in ocean currents that could make Europe’s climate resemble Labrador’s, the multiple effects from diminishing ice and snow fields, the release of stored methane from the ocean, and the release of carbon dioxide from Arctic tun-dra. The principle of prudence suggests that we not press our present systems to the limit, if only in order to have space to maneuver should unexpected changes reduce the productive capacity of our support systems.

The Intangibles. I once heard of a boy from a New York City ghetto who attended a city-owned summer camp in the hills. The bus arrived after dark, and when the boy stepped out, he looked up and said, “What are the little white things up there?” He had never seen stars. That, I submit, is deprivation. It worsens as cities grow and the sky gets murkier.

The Bottom Line. I think most writers on optimum population would agree that the optimum may be something like the numbers we passed around 1950: a world population of about 2.5 billion (40 percent of the present 6.4 billion) and a U.S. population of 150 million (half the present 293 million)—though any one of them might add the qualification “give or take a half” to those figures. Barring a catastrophe, even a determined worldwide effort would not reach the optimum in much less than a century.

The world is tending to divide into two different demographic regions. In the United States, the developing world, and particularly in Africa and the Middle East, population growth is on a path that will lead to catastrophe, hunger, and rising mortality. In Europe, Japan, South Korea, Taiwan, and Singapore, women have chosen to have far fewer children than would be necessary to replace themselves, and those countries are moving toward lower population levels. In fact, they face the question, how few is too few? But that is a topic for another paper.

Why such round Numbers?

Those are hardly rigorous calculations. They are full of horse-back arithmetic and value judgments—what living standard is “comfortable”? There will be unpredictable technological and environmental changes, some of which will further diminish the Earth’s support capability. But then, when do we know the exact consequences of any important national decision? All such choices must be made on the basis of partial information, subject to refinement as we proceed and learn more. For that reason, precision is not required here, nor is it reasonable to expect. If the weight of evidence suggests that the national population should be smaller than it is now, the policy implications are similar whether the gap is 100 million or 200 million. The key issue is to ask the question, in one context after another: “Would this problem be more easily solved with a smaller population or a larger one?” I think the examples above provide the answer.

Despite its inescapable imprecision, the effort to determine an optimum population is worthwhile. We need to show that human numbers matter in order to demonstrate the errors of growthmania. Contemporary debates about immigration, welfare, and tax policies too often ignore the population question—and thus dismiss the future. Defining a desirable population level is one step toward a more stable and less uncertain future. It sets the stage for the next necessary step: putting policies in place that will move human numbers in the right direction. ©2004 Lindsey Grant


1. David Herlihy, The Black Death and the Transformation of the West (Cambridge, Mass.: Harvard University Press, 1997).

2. Data from the U.S. Department of Agriculture, World Agriculture, Statistical Bulletin 861, November 1993. In the “New World,” I include the Western Hemisphere, Australia, and New Zealand. “Europe” excludes Russia.

3. “A great transition in human history will have begun when civilized man endeavors to assume conscious control (of population growth) in his own hands, away from the blind instinct of mere predominant survival.” J.M. Keynes, preface to Harold Wright, Population (London: Harcourt Brace, 1923.)

3. George Perkins Marsh, Man and Nature, or, Physical Geography as Modified by Human Action (originally published 1864. Reprinted Cambridge: Harvard University Press, 1965.)

5. Joint statement by the presidents of the U.S. National Academy of Sciences and the British Royal Society, released February 26, 1992, by the National Research Council, Washington.6. Paul D. Gottlieb, “Growth Without Growth: An Alternative Economic Development Goal for Metropolitan Areas” (Washington, D.C.: Brookings Institution Discussion Paper, February 2002, p. 25).

7. See E. F. Schumacher, Small Is Beautiful (London: Blond and Briggs, 1973; New York: Harper & Row, 1975–1989, p. 24). Evidence that the working classes have enjoyed little or, in some periods, none of the benefits of growth has been assembled by Richard Douthwaite in The Growth Illusion (Tulsa, Okla.: Council Oak Books, 1993; originally published in Great Britain by Green Books, 1992.)

8. For citations and a much fuller exploration of these limits, see Lindsey Grant et. al., Elephants in the Volkswagen (New York: W.H. Freeman, 1992); Lindsey Grant, Juggernaut (Santa Ana, Calif.: Seven Locks Press, 1996); Too Many People: The Case for Reversing Growth (Santa Ana, Calif.: Seven Locks Press, 2000); and “Diverging Demography, Converging Destinies” (Alexandria, Va.: Negative Population Growth, Inc., Forum Series, January 2003; also at www.npg.org.)

9. With the lower populations of 1950, total U.S. emissions would be 54 percent of the present 1.57 billion metric tons. Emissions by the rest of the industrial world would be 73 percent of 2.34 billion tons. Developing country emissions would be 35 percent of 2.53 billion tons. Totaled, world emissions from fossil energy would be 53 percent of the present 6.44 billion tons. (Data from U.N. Population Division and U.S. Department of Energy, Energy Information Agency, International Energy Annual, 2000.) Moreover, lower populations would mean less destruction of tropical forests, which presently add roughly 20 percent to world.

Lindsey Grant is a former National Security Council staff member and Deputy Assistant Secretary of State for Environment and Population Affairs. He has written extensively on population issues, much of it for or with the support of Negative Population Growth, Inc. His books include Elephants in the Volkswagen, a multidisciplinary effort to describe what U.S. population size would be desirable; How Many Americans?; and Too Many People: The Case for Reversing Growth.

Lindsey Grant

Lindsey Grant is a former National Security Council staff member and Deputy Assistant Secretary of State for Environment and Population Affairs. He has written extensively on population issues, much of it for or with the support of Negative Population Growth, Inc. His books include Elephants in the Volkswagen, a multidisciplinary effort to describe what U.S. population size would be desirable, How Many Americans?, and Too Many People: The Case for Reversing Growth.

Overcoming ‘Growthmania’ The very idea of defining an “optimum population” challenges centuries of economic and political assumptions that growth is by definition a good thing. So be it. The challenge of overcoming that assumption is at least as important as any optimum population number we may calculate. How ‘Growthmania’ Began Before the 1300s, unlimited growth …

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