Just 24 hours after admitting that he'd almost worked himself to death while making Tesla profitable, Elon Musk tweeted "There are way easier places to work, but nobody ever changed the world on 40 hours a week."

The motive behind the tweet is pretty obvious: It's in Musk's interest (at least according to conventional wisdom) to have his salaried employees believe that unpaid overtime is both inevitable and necessary.

Even so, his statement is ridiculous, both scientifically and mathematically. Let's start with the science:

  • Working more 40 hours a week is a huge health hazard. Long work hours (i.e., more than 40 hours a week) increase your risk of dying of heart disease by 10 percent. Furthermore, sitting for prolonged periods of time (like in front of a computer or in meetings) increases your risk of diabetes, cancer, and early death.
  • Working more than 40 hours a week can actually kill you. A recent study conducted by researchers at Stanford and Harvard concluded that "working long hours increased mortality by 20 percent." Assuming an average lifespan of 80 years, that means long work hours could trim as much as 16 years from the lifespan of the average worker.
  • Working more than 40 hours a week actually decreases productivity. Contrary to popular belief, demanding longer work hours decreases rather than increases the number of hours employees actually spend getting things done. In one landmark study, cutting work hours from 40 to 32 hours a week had no impact on their productivity.

So I suppose that, in a way, working long hours does change the world by reducing the surplus population, but that's about it. The important point here is that people who work 40 hours a week get as much done, on average, as those who work 60 hours a week. Maybe more.

But let's assume, for the sake of argument, that Musk's premise is correct and long work hours increase employee productivity. Even then, the notion that "nobody ever changed the world on 40 hours a week" is mathematically absurd.

If it takes one person 60 hours a week to change the world, then it would take two people 30 hours a week. Or one person could work 30 hours a week, in which case it would take twice as long to change the world.

One could argue, of course, that in business every company is racing against the competition to be the first to market. In that case, given the shortage of trained programmers and engineers, flogging the heck out of the ones you've got should get you first to market, right?

Maybe so (I'm skeptical), but history shows that being the first into a market isn't what it's cracked up to be. Who uses  VisiCalc or WordPerfect today? Or searches the web with AltaVista? Or drives the first electric car, which, incidentally, debuted in 1832? (Good bar bet there, BTW.)

Furthermore, the vast bulk of innovations in the 20th century--like the digital computer, the copy machine, graphical user interfaces--were accomplished inside companies where 40-hour workweeks were very much the norm.

Finally, and more important, Musk himself puts the lie to the notion that you can't change the world in less than 40 hours a week. Both SpaceX and Boring are potential world-changers, and Musk can't possibly be spending even 40 hours on either of them, not while running Tesla.

There's no question that Elon Musk is an engineering and management genius, but in this case he's either being self-interested or just plain silly.