Beware the taxicab fallacy
A study on the labor supply of New York City cabdrivers changed my life.1
Back when people actually hailed taxis, researchers followed a bunch of drivers to understand how long they chose to work. They found most drivers seemed to set a fixed target for each day: if a normal day brought in $120, they'd drive each day until they reached that amount. On average that meant eight hours, but it varied with demand—when the city was busy with passengers, they might be able to stop in just six hours; on rainy days, they might have to work 12.2
Sounds reasonable, right? Except the implication is that the drivers worked more hours precisely when they earned the least. When they worked six-hour days, they were earning $20/hour; when they worked 12-hour days, they were earning only $10/hour. If they'd flipped their hours—called it early on the tough day and worked late on the good one—they would have averaged $150 across the two days instead of $120! They'd suffer more volatility (making less than they needed one day and a lot more the next), but as long as they knew some good days were coming to balance out the bad ones, they'd end up ahead.
This comes up a lot in my own life. I'll naturally feel like I can’t stop working until I get a few things done every day, which would mean working longer hours when I'm less productive. By remembering the taxicab fallacy, I avoid that: I'll log off early on a tough day without feeling guilty, because I know I'll make it up and more by working hard when things are going well.
This doesn't work for all jobs. If you write a nightly column on the news of the day, or if you work on an assembly line where the next person is counting on you to install ten widgets per day, you have to produce the same quantity of work no matter how long it takes. But most work isn't like that; timelines are longer and there are fewer dependencies. Plus, some work can be transformed—if your nightly column doesn't have to be on the news of the day, you can work ahead on future pieces when you're feeling good and build up a buffer.
The bigger caveat: whereas the taxi drivers’ productivity was determined by external factors (the weather, passengers' behavior), your focus and energy is somewhat under your control: if you always give up when you're stuck, you won't get anything hard done. So you can't take this too far. (I've found it helps to force myself to get one small thing done before giving up, because that often unlocks momentum to do more.)
But if you have a track record of having plenty of productive days—and making the most of them—don't feel bad about slacking off when something comes up or when you just don't have it that day. Go do something fun.
This is a dangerous statement, because a lot of splashy behavioral findings like this one turn out not to replicate in future studies or analyses. The taxicab findings seem to have held up despite some back-and-forth, but if you want to be extra cautious, replace “study” with “parable” and I promise the rest of the piece still works.
Numbers here are illustrative, not exactly what the study found.
This tracks with a personal innovation in my own life that I call non-zero days. I define success as doing more than nothing, which keeps me from skipping just because I don't feel like it, but also let's me off the hook of that day just isn't going to work for me. I've found it helps in exercise, writing, and work.