Rationality, Flying and Driving to Work

Is it rational to fly and drive to work?

Herein, I’ll try to estimate probabilities and utilities.

Dying: With what chances would I take a $5000-to-life bet? I would definitely take a 1-in-a-million bet, and would definitely not take a 1-in-10,000 bet. So u($5000)>10e-6 * u(life).

First, flying: I’ll use my most recent flight as an example. I flew to spend a month with my family, including my toddler nephew. What’s the utility in that? Well, I am pretty sure I would answer “no” to someone offering me a 50-50 bet for $5000 to give up my flight, and yes to a 1-in-10 bet. So u($5000)<1/2 * u(flying). Hence, as long as the chances to die in an airplane crash are less than 1-in-500,000, I should be safe. My flight has two legs: west-coast-> east-coast, and east-coast -> .il. Let’s estimate those separately, and remember that less than 1 flight every three years in a commercial airline crashes: there are at least 100 planes landing in Israel every day, so 300,000 per year. There are even more flights west-coast -> east-coast per day. Therefore, it seems that it would be rational for me to fly (considering just the “flight risk” vs. “flight benefit”, not taking into account how  much the flight actually costs…but at least as a first estimate, this is convincing).

Next, driving to work. For the sake of this calculation, we’ll ignore the risk in other methods of getting to work, and also the utility of a non-fatal accident. In California, 1.2K car occupants die every year from accidents. Let’s assume every fifth Californian drives to work daily. That would make it 6Million drivers. The chance to die in a given year from a car accident is therefore bounded from below by 1-in-1000. I would probably make a 1-in-1000 bet against my life for $100,000. Assuming I drive to work 200 days a year, that would mean I should value the benefit of driving to work at >$75, meaning, I would not want to take a $75 for not driving to work. Given that not driving to work would mean: taking an extra 2 hours each way (not driving is not driving — not even to the train station!), as long as I value my time at more than $20/hour, it would make sense. It should come as no surprise that I do!

(Note: For the sake of simplicity, I did not do a full utility calculation — just “utility gained from driving/flying” vs. “chance to die”. A full calculation would depend on the utility I assign to things like “pollution”, for example. This is just a quick back-of-the-envelope to show that it is entirely reasonable for a rationalist to fly on airplanes and drive to work.)


One Response to Rationality, Flying and Driving to Work

  1. Leibovich says:

    You neglected the fact that there’s a (strong?) dependency between the risk of accident to the way you drive.

    Of course, the rest of the post doesn’t make sense at all, but I assumed it’s for entertainment purpose only 😉

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