The Sad Tale of Paul Ehrlich

Yesterday, I wrote about Why Jeff Bezos is Wrong in his calculations of future energy needs. Today I want to talk about the future population of planet earth.

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In my twenties, I was a graduate student at Stanford. I found Paul Ehrlich’s books and I believed Ehrlich was right that the population was going to explode and cause epidemics of mass misery. I read everything Paul wrote. I found him, and we started having lunches together at the Faculty Club once a year or so. I enjoyed learning from Paul and getting his wisdom on ecosystems and the dangers humanity faced in the future. He was always so urgent that the time to act is now! We don’t have a moment to lose! We must save the world from the population bomb before it’s too late!! Then after every lunch, he would finish off a piece of chocolate cake and I remember so clearly him scraping every last molecule of chocolate cake and icing off the plate until it was mirror clean. He loved chocolate cake, and it was a pleasure to watch how much he loved it.

The opposition to the population bomb was a guy named Julian Simon, who had a degree in marketing and was a mail-order marketing expert. He took on Ehrlich, who had a PhD, Stanford, many books, TV-show appearances, and tremendous press coverage. Simon explained that population was good, because more people created more brilliant scientists - Einsteins and Feynmans - who could figure out how to solve the problems of the future. His argument was that you don’t need many super bright people to change the world for the better, and those super-bright people would surely be more numerous if people had more children, not fewer. This was called the “cornucopia” theory, because you would get a bounty of benefits from a growing humanity that would surely be able to solve any future problem.

“Preposterous!” Paul would say, stabbing a crumb of chocolate cake with his fork. He and I used to used to make fun of the marketing guy who thought he could go up against the well-known scientist and his conclusions. Even though Malthus had predicted a population disaster for the 19th century that never happened, Paul was sure that “this time, it’s different,” now the numbers are just too scary, and we only have a limited amount of time to save humanity.

At this time, in 1980, Simon had no scientific credentials. So he challenged Paul to a bet. He said “Name any commodity and pick any date in the future more than a year from now, and I’ll bet you that the price of that commodity is lower in the future than it is today, adjusting for inflation.” So Paul picked five metals: chromium, copper, nickel, tin, and tungsten. He purchased $200 of each, for a total of $1,000, and he bet Simon that ten years later they would be worth much more, not much less. They agreed that the winner would pay the difference in price for the basket of metals after adjusting for inflation. Paul said this was easy money, like taking candy from a baby.

Ten years later, on an inflation-adjusted basis, all the metals were priced lower. Paul sent Simon a check for $576.07 to account for the drop in price.

The analysis is interesting. If the wager had been for 30 years rather than ten, Ehrlich would have won a bit of money. As with any such measurement, the starting and ending points matter. But, overall, on an inflation-adjusted basis, commodity prices do trend downward after adjusting for inflation.


Over the next twenty years, the population bomb fizzled. Paul predicted war, famine, starvation, mass suffering - he was wrong on all counts. He was wrong about other predictions as well. He was interesting to have lunch with, and he knew a lot about butterflies, but his life’s work - warning of an impending apocalypse - was based on poor analysis and a disregard of history. He continues to believe in his dire predictions today. “This time it’s different” - it usually isn’t. The earth’s resources are vast, and we continue to improve ways to extract, refine, and use them.

The moral of this story is that sometimes a dogged marketing professor can be more right than a fellow of the National Academy of the Sciences with hundreds of published papers. Here’s Alex Epstein, a philosopher, showing how Ehrlich and other serious scientists are often very wrong: