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.

population bomb cover.jpg

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:

Are you Curious or an Expert?

In the choice between changing one’s mind and proving there's no need to do so, most people get busy on the proof.
-John Kenneth Galbraith

This is the beginning of my new daily blog. I will send an email summary every Friday.

Have you read It’s my 20,000-word essay on building a reality-based view of the world. Looking at the comments and reading emails - it’s like people are reading two different essays. The comments are essentially similar to this one:

It’s a list of your opinions deliberately framed to get the reader to agree with you as their “starting point”. You do this by cherry-picking sources and links which bolster your position, and then, almost as a side-note, conceding that other research concludes differently. 

Yet the email responses are like these:

I found your essay through Marginal Revolution and I found your writing to be deeply thought-provoking and convincing. I would love to sign up to your newsletter, and I wish you all the best with your new project! - Daniel

It sums up so much of what I've read, watched, or otherwise consumed and had an inkling to agree with, but never had available as a resource in one spot. Thanks again for putting this outstanding and vital content out into the world. - Travis

I appreciate the time that you put into this and look forward to continuing hearing your words of wisdom. - Harold

First time i read an article to the end. How refreshing and interesting. Just loved it. Can’t wait for the newsletter. - Max

I think what happened is that experts read until they find something they disagree with, then they zoom to the bottom and leave a comment. Here is how I would summarize it:


In my experience, 95 percent of people respond to being wrong by getting busy proving that they are not. But five percent go toward the source of error. Either they find the exact error and understand it, or they adjust their view of the world to incorporate the new data. I have no problem with people telling me something is wrong, but they need to show the data and the analysis, not call names.

A few people are curious experts. They don’t mind being wrong, because it gives them a chance to update their worldview. If you are inquisitive and you think being wrong is your path to learning, you’re in the right place. Vote and tell me what kind of person you are:

Tell the truth (it's anonymous, no one will ever know):

The other day, I told my brother I thought there were more than 1,000 shoe stores in New York City. He shrugged. I met him the next day and told him that the only data available was the number of chain shoe stores in the city: 250, down from about 15 percent more several years earlier as a result of Zappos and the retail-pocalypse. I therefore concluded that there were probably 400-700 total shoe stores in New York and I was officially wrong.

I am wrong all the time. I am trying to be less wrong, but it’s a lifelong process.

If you haven’t read my essay yet, please go to Inreality.Show. Give me 15 minutes a day and I’ll try to make you less wrong, too. I’ll be back tomorrow with more tools to help cut through the noise.