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In 1980, the ecologist Paul Ehrlich entered into a dramatic bet with the economist Julian Simon. Insisting that population growth would produce scarcity, Ehrlich wagered that the prices of five specified metals would increase over the next decade. Insisting that innovation in methods of finding, extracting, and using the metals would increase supply, Simon bet that the prices of those metals would decrease. The two meant their bet to test a larger question: Is population growth a serious problem, particularly in its effects on available resources? Ehrlich thought yes; Simon thought no; and they agreed that the bet would help to establish who was right. For over three decades, observers have seen the Ehrlich-Simon bet as raising other questions as well: Are conservatives wrong to think that technological innovation and free markets are likely to solve our problems? Are liberals wrong to emphasize the importance of conservation and limits to growth? Are environmentalists full of nonsense?

As it happened, Simon won the bet. Because of his victory, he became a conservative hero. He died in 1998, but he continues to be invoked by countless people who celebrate innovation and growth and who denounce what they see as environmentalist hysteria (not least with respect to climate change, a problem that Simon himself dismissed). Since 2001, the Competitive Enterprise Institute has awarded an annual Julian L. Simon Award, celebrating Simon’s work “debunk[ing] the alarmist predictions of eco-doomsayers like Paul Ehrlich.”

Paul Sabin, a professor of history at Yale, regards the bet as historically important. The Bet makes a convincing case that the debate between Ehrlich and Simon illuminates central issues of its era. Sabin contends that Jimmy Carter’s conservation-centered approach to energy and the environment grew partly out of ideas that Ehrlich promoted, and that Ronald Reagan’s pro-growth approach was influenced by Simon. The two different orientations are very much with us today. With their contrasting narratives of looming environmental catastrophe and techno-optimism, they define important strands of the Democratic and Republican parties and indeed of American culture.

Paul Ehrlich was (and remains) a distinguished scientist, specializing in ecology. Much of his academic work involves butterflies. In 1968, he published a runaway best seller called The Population Bomb, which had twenty-two reprintings in its first three years. The first words of the book sounded the alarm: “The battle to feed all of humanity is over…. At this late date nothing can prevent a substantial increase in the world death rate.” Ehrlich warned of “famines of unbelievable proportions” occurring by 1975 and of “hundreds of millions of people” starving to death in the 1970s and 1980s. In 1969, Ehrlich published an essay called “Eco-Catastrophe!” in which he contended that the inevitable result of the imbalance between the rate of birth and the rate of death would be the “greatest cataclysm in the history of man.” In 1970, he predicted that Americans would be subjected to water rationing by 1974 and food rationing by the end of the decade, and contended that within ten or twenty years, all marine fishing might cease because of irreversible changes in the oceans. He claimed, “If I were a gambler, I would take even money that England will not exist in the year 2000.” He raised the possibility that because of DDT and other pesticides, Americans’ life expectancy might fall to forty-two by 1980.

Notwithstanding the dire nature of his warnings, Ehrlich insisted that a great deal could be done to reduce the damage. He proposed that the United States should establish a powerful Bureau of Population and Environment, which “should be set up to determine the optimum population size for the United States and devise measures to establish it.” He noted that many of his colleagues favored “some sort of compulsory birth regulation,” including “temporary sterilants to water supplies or staple food,” but he dismissed that approach as impractical, and argued instead for “financial rewards and penalties designed to discourage reproduction.”

He endorsed luxury taxes on cribs, diapers, baby bottles, and baby foods, and he urged that the bureau should seek some method “to guarantee that first-born children were males” (because some couples are more likely to have more children if their first-born is female). Soon after publication of The Population Bomb, he helped to create a new organization, called Zero Population Growth, designed to promote public awareness and to address the problem. (Sabin notes, apparently without irony, that Ehlich and his colleagues “dreamed up Zero Population Growth after a game of squash in New Haven.”)

Ehrlich became a national celebrity. He was featured on prominent television programs, and his arguments about overpopulation attracted worldwide attention. On The Tonight Show with Johnny Carson, he said that it was “already too late to avoid famines that will kill millions.” He appeared on Carson’s program at least twenty times, wrote a column for the Saturday Review, and contributed regularly to both Penthouse and Playboy. In 1970 alone, he appeared on two hundred television and radio shows (and also gave one hundred public lectures).


However apocalyptic his message, Ehrlich was entertaining, extroverted. passionate, gregarious, charming, and charismatic. A friend’s first impression was that Ehrlich was “funny as hell.” Despite his distinguished academic work, he claimed that in college, he majored in “liquor and women.” He reported, “I didn’t stand up one day and say, ‘My God, I’m going to get everybody to stop [fuck]ing.’ It’s sort of one thing led to another.” He liked to joke, “What do you call people who use the rhythm method? Parents.” He publicized his own vasectomy (and even included it in his byline for a 1970 article).

In Sabin’s telling, Ehrlich’s extraordinary popularity allowed him to arrive “where he wanted to be, on center stage, with a large and interested public audience.” In Ehrlich’s own words, “The book is giving me a lot of opportunity to shoot my mouth off over the public media, and I am determined to take full advantage of it.” He argued in favor of a “relaxed lifestyle, good friends, and a happy sex life” instead of fame and profit. But he did not appear indifferent to fame, and his own rhetoric was not exactly relaxed. He knew how to make enemies, describing some of his opponents as “clowns,” “morons,” and “idiots.”

Julian Simon was an obscure, introverted, socially awkward economist at the University of Illinois, Urbana, who struggled with serious depression for more than a decade. (In his own words, “I refrained from killing myself only because I believed that my children needed me, just as all children need their father.”) Simon was certain that Ehrlich was wrong. In his view, technological solutions could prevent scarcity and famines, even with large population increases. Having once been concerned about overpopulation himself, he had a convert’s zeal.

The conversion was inspired by what he saw as a kind of epiphany, which he experienced while remembering a moving speech by a Jewish chaplain over the dead on the battlefield at Iwo Jima. In that speech, the chaplain mourned the loss of potential human talent and promise. Simon recalled, “I thought: Have I gone crazy? What business do I have trying to help arrange it that fewer human beings will be born, each one of whom might be a Mozart or a Michelangelo or an Einstein—or simply a joy to his or her family and community, and a person who will enjoy life?”

Witnessing Ehrlich’s growing fame, Simon was simultaneously aghast and envious. As Sabin writes, “Here he was, sitting and grumbling alone in his living room, while the most beloved television host in the country regarded Paul Ehrlich, as Simon later complained, with ‘a look of stupefied admiration.’” Simon seethed. “What could I do? Go talk to five people? Here was a guy reaching a vast audience, leading this juggernaut of environmentalist hysteria, and I felt utterly helpless.”

In 1970, Simon agreed to give a little talk in Urbana, under the title “Science Does Not Show There Is Over-Population.” He argued that for the human race, population growth was a triumph, not a disaster. The talk received some local attention, and he was invited to speak to somewhat larger groups, which led him to develop his view in academic articles, where he emphasized the importance and the inevitability of technological innovation.

Simon argued that such innovation would increase both efficiency and supply, and that population growth could not be said to be harmful. In fact, larger populations could increase investment and make it easier to provide infrastructure. Human beings are not butterflies, and even if their population is growing rapidly, they can avoid shortages and increase abundance through the price system, which promotes investment, discovery, and invention. (This is, in a nutshell, the economist’s response to the ecologist.) But Simon’s small voice was drowned out by prominent work coming to the opposite conclusion, including the influential book The Limits to Growth, published by the Club of Rome in 1972, which sounded a loud alarm very much like Ehrlich’s.

Simon did not give up. Describing Ehrlich’s views as “morally abhorrent,” he insisted that “there are no ultimate limits” and that resources are becoming ever more abundant. He denounced “false statements of bad news” and claims about coming eco-catastrophes that were “downright misleading.” In 1981, he attacked Ehrlich in the Social Science Quarterly, asking, “How often does a prophet have to be wrong before we no longer believe that he or she is a true prophet?” Objecting that Ehrlich had repeatedly made false predictions without facing the consequences, he proposed that the two of them bet on the prices of raw materials. If Ehrlich was right to think that population growth would lead to scarcity, prices should increase. But if Simon was right to think that technological innovation would prevent scarcity, prices would go down. Simon went so far as allow Ehrlich to select the raw materials on which he would like to bet.


Ehrlich was delighted. He said that he would accept Simon’s “astonishing offer before other greedy people jump in.” Working with like-minded scientists, he chose five metals of considerable economic importance: chromium, copper, nickel, tin, and tungsten. In the 1970s, the market prices of all five had increased significantly, at least in nominal terms, and Ehrlich was confident that the trend would continue. The bet was for $200 for each of the five metals, with the winner determined by whether the price increased, adjusting for inflation. The Chronicle of Higher Education called it “the scholarly wager of the decade.” (True, there wasn’t a lot of competition for that particular honor.)

Over the next decade, Ehrlich and Simon continued their respective crusades. Ehrlich became a prominent and persistent critic of the Reagan administration. The once-obscure Simon became a national figure and a hero to the right. Appointed as a senior fellow at the Heritage Foundation, he moved to the University of Maryland, where he hoped “to try to sell some views on public policies.” To that end, he attacked the United Nations Fund for Population Activities as hopelessly biased, and he warned darkly that the “population lobby” was using the issue of abortion to cover its real concern, which was population control. Two articles about him appeared in The Washington Post, with the second carrying the title, “The Heretic Becomes Respectable.” He was featured on national television, appearing on The MacNeil-Lehrer News Hour and Firing Line (hosted by William F. Buckley Jr.).


Dan Borris/Corbis

Julian Simon, with objects made from the metals in his bet with Paul Ehrlich, 1990

In October 1990, Simon found a small envelope in the mail from Palo Alto. The envelope contained a piece of paper with metal prices and a check from Paul Ehrlich. Ehrlich included no note. In the 1980s, more people had been added to the planet than in any decade in the history of the world (800 million). Nonetheless, the prices of every one of the five metals declined, and by an average of 50 percent. Simon seemed to have been vindicated. Large increases in population need not lead to scarcity.

Ehrlich did not see things that way. In his view, he had been wrong to agree to the ten-year time line, which was just too short; eventually prices would indeed rise. In his view, “Julian Simon is like the guy who jumps off the Empire State Building and says how great things are going so far as he passes the 10th floor.” What Ehrlich did not say, but what economists have now established, is that Simon was lucky. A few years ago, economists ran a series of simulations for every ten-year period from 1900 to 2008, and they found that Ehrlich would have won no less than 63 percent of the time.

Does this mean that Ehrlich was essentially right? Not at all. In the aftermath of World War I, the United States experienced a sudden collapse in the prices of commodities, and it took a long time for them to climb back from their low levels. Macroeconomic cycles, and not scarcity, produced the general increase in prices from their postwar low. Indeed, Simon’s victorious prediction about the 1980s stemmed largely from macroeconomic factors; a late-decade recession helped lower prices. Commodity prices are highly volatile, and they are a poor proxy for the effects of population increases. Simon and Ehrlich both believed that their bet would be a good test of their competing views on population growth. But on that point, both of them were wrong. With respect to the question that divided them, their famous bet established very little.

Nonetheless, Simon was emboldened by his well-publicized victory, and he became an increasingly prominent national figure, writing for the public rather than in academic journals. In 1995, he took to the pages of the San Francisco Chronicle to denounce the “doomsaying environmentalists,” specifically naming Ehrlich. He insisted that by every measure, “material and environmental welfare in the United States and the world has improved rather than deteriorated.” He also castigated Vice President Al Gore, describing his book Earth in the Balance as an “ignorant and wrongheaded collection of clichés.” Simon proposed a new wager: in his view, any trend related to human welfare would get better rather than worse. He asked: Who would take the bet?

Ehrlich was eager to do so. Working with Stanford climatologist Stephen Schneider, Ehrlich invited Simon to wager on fifteen critical “indicators,” including global temperatures, concentrations of carbon dioxide, tropical forest area, and quantities of rice, wheat, and fish per person. Simon declined the offer, insisting that the focus should not be on “indicators” but more directly on human welfare (as measured, for example, by life expectancy or purchasing power). Simon agreed that the physical world might change, perhaps for the worse, but he insisted that human progress would continue. Ehrlich responded that Simon was “clueless,” because he did not “understand anything about risk, trends or things that affect human welfare.” In Ehrlich’s view, it is necessary to “focus on negative environmental or social trends because they are the ones that need to be fixed regardless of whether other trends are positive.”

As the years went by, their rhetoric got uglier. Ehrlich told a Wall Street Journal reporter, “If Simon disappeared from the face of the earth, that would be great for humanity.” Simon’s response: “I already know I’m a jerk. But I’ve been right every time.” Simon dismissed Ehrlich as “shameless,” “arrogant,” and an “unblemished failure.” Ehrlich characterized Simon as a “flat earther” and argued that Simon was engaged in a “brownlash,” defined as “the deliberate attempt to minimize the seriousness of environmental problems through misuse or misreporting of science.” Sabin notes that those who participate in a serious debate can “hone each other’s arguments so that they are sharper and better,” but with more than a touch of understatement, he observes that the “opposite happened with Paul Ehrlich and Julian Simon.”

Sabin very clearly and usefully connects the dispute between Ehrlich and Simon with recent and current debates about environmental issues. Some people are strongly drawn to Ehrlich, and others to Simon, and the two camps define not only the political poles, but also significant segments of the Democratic and Republican parties. True, population growth is no longer the central issue it was during the 1970s, but consider the problem of climate change, where the opposing positions have an unmistakable connection with those laid out by Ehrlich and Simon. Indeed, Ehrlich has insisted, and continues to insist, that the risks associated with climate change are very grave (and have a great deal to do with population growth). Not surprisingly, Simon dismissed those same risks.

Sabin himself refrains from taking sides. He commends Ehrlich for helping to alert people to numerous environmental dangers. At the same time, he thinks that Simon persuasively demonstrated that human creativity and market forces produce unanticipated adjustments, defying apocalyptic pronouncements. Noting that history has repeatedly falsified Ehrlich’s predictions, Sabin insists that the idea of “natural limits” must be subject to skeptical scrutiny. But as Sabin emphasizes, Simon never acknowledged the extent to which significant social improvements, including cleaner air and water, have occurred in part because of regulatory requirements favored by environmentalists, including Ehrlich himself.

For all their differences, Ehrlich and Simon claimed to agree on the overriding importance of evidence and facts. This is ironic, because too much of the time, both of them spoke and wrote as men of faith rather than science—mirror images of one another, so interested in public attention, and so intransigently committed to their own large, headline-grabbing dogmas, that they seemed incapable of learning and impervious to counterarguments. To use Isaiah Berlin’s terminology, they were hedgehogs, knowing one big thing, when environmental problems are best investigated by foxes, questioning abstract theories, nimble, and insistent on the importance of the details.

Ehrlich was the worse offender here. On the question of population growth, he never confronted Simon’s arguments. (As late as 2009, Ehrlich published an article with the title “Population: Enough of Us Now.”) But Simon was far too quick to conclude, from his work on that question, that environmental concerns are generally baseless. For example, destruction of the ozone layer posed extremely serious risks, with the science and the economics ultimately persuading Ronald Reagan to sign the Montreal Protocol in 1988 (which was strongly supported by Margaret Thatcher as well). Rejecting the scientific evidence as late as 1996, Simon wrongly insisted that the ozone problem is “simply another transient concern, barely worthy of consideration.” Also in 1996, Simon used the same words to describe climate change:

Given the history of such environmental scares—over all of human history—my guess is that global warming is likely to be simply another transient concern, barely worthy of consideration ten years from now.

Simon liked to say that his own predictions were accurate, and many of them were—but not all of them, and certainly not this one.

Simon was entirely right to emphasize the potential benefits of adaptation, including technological innovation. The best work on climate change, including that of the Yale economist William Nordhaus, does not ignore those effects but instead places considerable emphasis on them.* Such work pays attention to worst-case scenarios, but it does not speak of a pending apocalypse, and it does not take technological solutions as inevitable. Instead it acknowledges uncertainty and grapples seriously with both the benefits and the costs of various efforts to reduce the risks associated with a warmer world.

Sabin demonstrates that for all their faults, both Ehrlich and Simon made real contributions. But too much of the time, they were driven by grand, abstract narratives about history’s supposed arc. In dealing with the changing environment, as elsewhere, such narratives tend to be an obstacle to both understanding and progress.