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The Peculiar Blindness Of Experts

Credentialed authorities are comically bad at predicting the future. But reliable forecasting is possible.

David Epstein

THE BET WAS ON, and it was over the fate of humanity. On one side was the Stanford biologist Paul R. Ehrlich. In his 1968 best seller, The Population Bomb, Ehrlich insisted that it was too late to prevent a doomsday apocalypse resulting from overpopulation. Resource shortages would cause hundreds of millions of starvation deaths within a decade. It was cold, hard math: The human population was growing exponentially; the food supply was not. Ehrlich was an accomplished butterfly specialist. He knew that nature did not regulate animal populations delicately. Populations exploded, blowing past the available resources, and then crashed.

In his book, Ehrlich played out hypothetical scenarios that represented “the kinds of disasters that will occur.” In the worst-case scenario, famine rages across the planet. Russia, China, and the United States are dragged into nuclear war, and the resulting environmental degradation soon extinguishes the human race. In the “cheerful” scenario, population controls begin. Famine spreads, and countries teeter, but the major death wave ends in the mid-1980s. Only half a billion or so people die of starvation. “I challenge you to create one more optimistic,” Ehrlich wrote, adding that he would not count scenarios involving benevolent aliens bearing care packages.

The economist Julian Simon took up Ehrlich’s challenge. Technology— watercontrol techniques, hybridized seeds, management strategies— had revolutionized agriculture, and global crop yields were increasing. To Simon, more people meant more good ideas about how to achieve a sustainable future. So he proposed a wager. Ehrlich could choose five metals that he expected to become more expensive as resources were depleted and chaos ensued over the next decade. Both men agreed that commodity prices were a fine proxy for the effects of population growth, and they set the stakes at $1,000 worth of Ehrlich’s five metals. If, 10 years hence, prices had gone down, Ehrlich would have to pay the difference in value to Simon. If prices went up, Simon would be on the hook for the difference. The bet was made official in 1980.

In October 1990, Simon found a check for $576.07 in his mailbox. Ehrlich got smoked. The price of every one of the metals had declined. In the 1960s, 50 out of every 100,000 global citizens died annually from famine; by the 1990s, that number was 2.6.

Ehrlich’s starvation predictions were almost comically bad. And yet, the very same year he conceded the bet, Ehrlich doubled down in another book, with another prediction that would prove untrue: Sure, his timeline had been a little off, he wrote, but “now the population bomb has detonated.” Despite one erroneous prediction after another, Ehrlich amassed an enormous following and received prestigious awards. Simon, meanwhile, became a standard-bearer for scholars who felt that Ehrlich had ignored economic principles. The kind of excessive regulations Ehrlich advocated, the Simon camp argued, would quell the very innovation that had delivered humanity from catastrophe. Both men became luminaries in their respective domains. Both were mistaken.

When economists later examined metal prices for every 10-year window from 1900 to 2008, during which time the world population quadrupled, they saw that Ehrlich would have won the bet 62 percent of the time. The catch: Commodity prices are a poor gauge of population effects, particularly over a single decade. The variable that both men were certain would vindicate their worldviews actually had little to do with those views. Prices waxed and waned with macro economic cycles.

Yet both men dug in. Each declared his faith in science and the undisputed primacy of facts. And each continued to miss the value of the other’s ideas. Ehrlich was wrong about the apocalypse, but right on aspects of environmental degradation. Simon was right about the influence of human ingenuity on food and energy supplies, but wrong in claiming that improvements in air and water quality validated his theories. Ironically, those improvements were bolstered through regulations pressed by Ehrlich and others.

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June 2019