What Bothers People About SuperFreakonomics?

We never know what parts of our books will agitate people enough that they will send us an email. In Freakonomics, the passages that inspired the most emails were the discussions of swimming pools vs. guns and real estate agents not always acting on behalf of their clients.

In SuperFreakonomics, far and away the most common subject of emails is drunk walking vs. drunk driving. In particular, every few days someone writes us to tell us that our analysis is wrong because we are comparing the rate of death per mile driven drunk versus the rate of death per mile walked drunk. Sure, they say, drunk walkers get killed more per mile. But since cars travel much faster, per hour, it is safer to drive drunk than to walk drunk.

It is true that if someone held a gun to your head and said, “If you don’t walk drunk for an hour or drive drunk for an hour, I will shoot you. You choose whether you would walk or drive,” then you might very well want to spend your hour walking drunk. However, in real life, that is virtually never the dilemma you face. Rather, you are drunk in one place and you want to get to another place. The distance you need to cover is what is constant, not the time you will spend traveling.

Thus the per-mile comparison we make is the most sensible one.

The other thing about that passage that makes people angry is that they interpret our arguments as condoning drunk driving, despite the fact that we cite my own research that shows that drunk drivers are 13 times as likely to cause a fatal crash. We end by telling people to take a cab.

When we wrote that people should take a cab, however, we never actually did the calculation. Is it really true that taking a cab is the right thing to do?

According to our estimates, there are 21 billion miles driven drunk each year, resulting in 13,000 fatalities. That works out to be about one fatality for every 1.6 million miles driven drunk.

Economists typically use a value per statistical life of $6 million. So, for instance, when trying to decide whether the benefits of a government program outweigh the costs, the benefit per life saved is calculated as being worth $6 million. If one person dies for every 1.6 million miles driven drunk, and the value of a life is $6 million, then the cost in extra deaths per mile driven drunk works out to be about $3.75.

That number is an average. Obviously, it will depend on how drunk you are, and it ignores other risks associated with driving drunk like getting arrested.

How much does it cost to take a cab? According to this web site, a three-mile cab ride will cost you about $8 plus tip in most major cities. After a tip, that is about $3 per mile — not too different than the implied cost per mile of driving drunk.

Obviously, I’ve left out all sorts of other costs and benefits in this simple analysis that could tip the balance one way or another, but I suspect most people will be surprised to see how close it is to a toss-up.

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  1. Ramsey H says:

    The real problem with your analysis is that I don’t care if some drunk idiot gets himself killed while walking. I *do* care if a drunk driver kills someone *else*.

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  2. rusty says:

    I don’t know about you, but my choice of where to go is normally constrained by my means of transportation. It’s not a question of walking out of a bar and randomly being assigned to the Car or No Car group. When I have to walk home, I tend to stay closer to home; when someone is DDing, we feel free to choose places that are further afield.

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  3. Adam says:

    Another consideration here is one of internalization — the cost in drunk driving is more likely to be an externality, while the cost of a cab is internalized by the drunk. Cab use thus should make the intoxication-transportation market more efficient.

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  4. Phil says:

    The dollar analysis is incorrect because you are comparing the government cost of a life vs. my out of pocket cost for a cab. Would you sacrifice your life or your spouse’s or children’s life for 6 million dollars? Probably not.

    The government and I don’t spend money on the same scale, so to compare the two is not valid.

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  5. Phil says:

    Depends how drunk, doesn’t it? What is the threshold you use for drunkenness? BAC of 0.08?

    I bet the death rate rises more than linearly as BAC rises, so maybe driving at 0.08 is actually safer than cabbing it.

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  6. Dan says:

    Considering that I typically don’t walk distances over a mile (especially drunk), I don’t see driving and walking as substitutes. But If I were to walk the distances that I might otherwise drive, I would become less drunk over time, making the long walk safer as the walk gets longer. And I’m still struggling to see why this is a topic worth discussing. I guess I should just move on.

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  7. Tim says:

    While the distance is constant in either case, the time spent traveling should matter since the effect of alcohol diminishes over time.

    Also as another commenter noticed…when driving it isn’t always the drunk who pays the cost of an accident. Plenty of otherwise uninvolved people are killed by drunk drivers every year, and I’d be willing to bet very few are killed by drunk walkers.

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  8. Eric Valpey says:

    Except the choice is rarely so simple.

    Oftentimes, the decision of how to travel home informs the decision of where to go in the first place.

    If one expects to walk home, one will only really be considering a local bar/pub within walking distance. Making arrangements for a designated driver or planning on public transportation alters the landscape of evening destinations.

    “Walking home” may actually be some combination of walking and public transit (walk to a transit station – bus/rail to local station – walk home). Thus the number of miles actually walked is far fewer than the number of miles driven by car or by cab.

    If we are talking about someone who is surprised to find themselves drunk at a bar who has traveled there by car and now must choose how to get home the options might include a nearby destination other than home like a friend’s house or a late night diner where one might conceivably sober up; another example where “walking” might involve alternate paths.

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