The positive externalities of Eminem

And I probably ruined your parents’ life
And your childhood too
‘Cause if I’m the music that y’all grew up on
I’m responsible for you retarded fools
I’m the super villain Dad and Mom was losin’ their marbles to
You marvel that? Eddie Brock is you
And I’m the suit, so call me—

Eminem, 2021, Venom

In complex systems you can’t do one thing. When he was chief economist of Uber, John List and his team ran an experiment to see how tips affected drivers. They rolled out the option to tip in four cities and collected the data. Tips, List wrote, work. When drivers earned more they drove more. But you can’t do just one thing. When tipping expanded to other markets other drivers drove more too. With the increase supply of drivers but the same demand, total earnings with tips were about the same as before. But the drivers ended up working more. It was more per ride but fewer rides.

As a teen I remember big concerns about what music teens listened to. In 1990 the parental advisory label started to appear on CDs. In 1997 Eminem release The Slim Shady LP. That music was for my car only, not the house. Eminem gets this. “I’m the super villain Dad and Mom was losin’ their marbles to”. It was NOT GOOD that we were listening to this.


List’s Uber experiment explains an externality. Do one thing and this other thing happens too. Eminem’s other thing is health. Venom is my favorite workout song and Eminem is the 13th most popular artist on Spotify with fifty-three million plays. A month! That’s 100k hours a day. If one-fourth of those hours are someone exercising, that’s 14,000 pounds lost each month.

Behavior change starts with easily understood stories. Tell someone a story they agree with, or understand, or can tell to others (which raises their status). Eminem’s explicit lyrics are something to warn against. But telling a positive story through some Fermi thinking sounds good too.

Fermi questions, answers, and landmarks

A Fermi question is something like, How many rolls of toilet paper do the residents of Columbus Ohio use in a week? Fermi questions are silly but embody some serious thought. Namely, how do we think about the world?

There’s some fun little math behind a Fermi question but the hardest part is often the start. For instance, how many people live in Columbus Ohio? Tim Harford knows. Rather, Tim Harford has a suggestion.

“Andrew Elliott—an entrepreneur who likes the question so much he published a book with the title Is That a Big Number?—suggests that we should all carry a few ‘landmark numbers’.”

Landmark numbers are figures we can use to guide our thoughts about the world. For instance, there are about four million Americans at any age under sixty. New York City has a population of about nine million. Columbus Ohio has a population of about one million. This is actually quite helpful just for a start.

Using a Zeckhauser maxim, “when you are having trouble getting your thinking straight, go to a simple case.” If every resident of Columbus Ohio used half a roll a week, how many rolls of toilet paper would they use? That’s easy! We have a million people, each uses half a roll, and that’s 500,000 rolls per week. No wonder we had a shortage.

Tsk tsk, Enrico Fermi would scold us. You can do better. And indeed we can. That is the point of thinking about Fermi questions. We can do better and even if we make a mistake, even if we make a few mistakes, we can still very likely be right. The reason is because of the random walk nature of our guesses. Some of our guesses will be too high (Columbus actually has 898,000 residents) and some will be too low, but overall these kinda-sorta balance out and that puts us in the right ballpark. Not only that, but making additional steps doesn’t necessarily mean additional steps in error. That, and more examples are here.

Good decision making takes nouns and verbs. We’ve got good verbs like inversion, mean reversion, extreme examples, and such. Landmark numbers give us a few nouns to work with too.

The very good Fermi book inspired this post: Fermi Knowledge.