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jkaufman comments on Wear a Helmet While Driving a Car - Less Wrong Discussion

47 Post author: James_Miller 30 July 2015 04:36PM

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Comment author: jkaufman 31 July 2015 05:13:20PM *  6 points [-]

When I looked into this a few years ago I turned up Prevention of Head Injuries to Car Occupants: An Investigation of Interior Padding Options (McLean et. al. 1997). The improvement in interior padding and airbags since 1997 is probably enough to bring the benefit of a bicycle-style helmet down to just a few percent injury reduction.

But even assuming its as high as 10%, Nick Beckstead wrote:

You allegedly get 1 micromort from driving 230 miles. Say that takes 4 hours, and say you get to reduce 10% of that by wearing the helmet. Then wearing a helmet for 1 hr saves your life with probability 1 in 40 million. So the question is whether you prefer a 1 in 40 million chance of saving your life or the convenience of not wearing a helmet in the car for an hour.

If you valued your life at $40M, then the question would reduce to whether you would be willing to wear a helmet for an hour if it saved you a dollar (neglecting safety benefits). I wouldn't wear a helmet for an hour for a dollar, and would pay a dollar to avoid wearing the helmet. Since all these estimates are average or conservative, that suggests it is not worth it to wear a helmet (at least for me).

Comment author: gwern 31 July 2015 08:13:22PM *  12 points [-]

I don't believe Nick's introspection here. $1/hour may sound plausible considered as a single choice for 1 hour, but not repeated, as it would be, over a lifetime: if you spend 3 hours a day in a car (which I have for a large period of my life), then he's willing to pay 3 * 365 = $1.1k a year or easily $50k over a lifetime to not wear a helmet? To put this in further perspective, the median American household's income is around that; so by claiming $1/hr, he is implicitly claiming other things like 'if a law were passed mandating wearing a helmet, I and my household would gladly labor like a slave for a year in exchange for an exemption', and so on and so forth. (You can quibble about things like discounting and Nick's probable above-median income and how many hours he actually spends in a car but still - $1/hr is actually quite a bit!)

Further, realistically, habituation and the hedonic treadmill means he would very quickly get used to it as a habit and eventually even come to expect it - like people get used to yarmulkes or old-timey men felt naked without their hats or the deaf/hearing-impaired get so used to their hearing-aids that they forget they are wearing them or how orthodontic patients can survive even the notorious and extremely unpleasant 'head gear'. Or more pertinently, they have already adapted quite nicely to car safety devices far more intrusive, restrictive, and unpleasant than a lightweight helmet: three-point seatbelts.

I am sure Nick really does dislike wearing a helmet to some degree (at least during the adaptation period...), but -$1/hr? No.

Comment author: jkaufman 07 August 2015 07:21:29PM 2 points [-]

if you spend 3 hours a day in a car

That's a lot more than most people do. Conservatively assuming that all travel is via car, the 2014 average on the American Time Use Survey [1] is 1.11hr/day [2]. At $1 = 1hr, that's $1.11/day.

But I do agree habituation is significant here. People probably felt similarly about seatbelts but I don't notice mine.

[1] http://www.bls.gov/tus/tables/a1_2014.pdf

[2] Broken down as, in hours per day: 0.02 for personal care, 0.10 for eating and drinking, 0.04 for household activities, 0.27 for purchasing goods and services, 0.08 for caring for and helping household members, 0.05 for non-household members, 0.27 for work, 0.03 for education, 0.04 for organizational, religious, and civic activities, 0.21 for leisure and sports.

Comment author: FrameBenignly 01 August 2015 06:48:25PM 0 points [-]

$50k a year times 40 years equals $2 million. He's maybe overestimating the price he's willing to pay, but he's also overestimating how much people typically value their lives at. You're also using a really high estimate for number of hours in the car. 3 x 365 x 60 = 32,850 miles per year.

Comment author: gwern 01 August 2015 08:00:59PM *  3 points [-]

I did not say $50k a year, I said $50k over a lifetime ($1.1k times around 40-50ish years, since you spend many of the early ones strapped in and driving tends to decline in old age; and honestly I don't want to project out past 2060 as it is).

You're also using a really high estimate for number of hours in the car. 3 x 365 x 60 = 32,850 miles per year.

I don't think that is extreme. As I said, I commuted that much for 4 years, and my dad spent most of his career with a 2h+ commute just for work, never mind all the other driving entailed in suburban life. Americans drive a lot.

Comment author: FrameBenignly 01 August 2015 08:20:33PM 2 points [-]

No, $2 million is median household lifetime earnings if they work for a typical 40 years which is way below the $40 million he's estimating.

Also, you just named two examples of outliers and suggested they were representative of your entire experience. Just glancing at estimates, most are between 10000 and 15000 miles per year as typical for Americans. Europeans are probably lower.

Also, Nick overestimated average driving speed which means he's even further overestimating the cost of not wearing a helmet. I calced it at around $50 per year; $.20 per hour.

Comment author: jkaufman 07 August 2015 07:09:35PM *  2 points [-]

3 x 365 x 60 = 32,850 miles per year.

Why are you assuming an average speed of 60mph? Most people's commutes have a lot more traffic than that.

Also, 336560 is 65,700 not 32,850.

The average person spends something like 1hr/day in a car, and travels an average of 13476 miles/year which gives us more like 36 mph.

Comment author: FrameBenignly 07 August 2015 07:56:03PM *  0 points [-]

The original estimate which gwern based his analysis on used a speed of about 60 mph, which is necessary to use when reversing the calculation back into miles. I would agree average speeds are probably lower.

Edit: I just noticed my calculation was wrong. I'm not sure where I got 32850 from. It's more like 60 something thousand. Whoops.

Comment author: jkaufman 09 August 2015 02:18:29PM 0 points [-]

Sorry, I'm not seeing where gwern uses 60mph?

Comment author: FrameBenignly 09 August 2015 04:00:47PM *  0 points [-]

He's making a calculation using hours based on an analysis originally written in micromorts per mile. He has to convert from miles to hours to do that. He uses the estimate you gave him which assumed 57.5 mph to be exact to make that conversion. I used 60 as a rough approximation. To calculate the miles he's using for his analysis, I have to use the same estimate. It's an unstated assumption gwern makes to get to $50k in a lifetime. A lower average speed would make Nick's argument stronger and gwern's cost estimate lower.

Comment author: ChristianKl 03 August 2015 08:58:01AM 0 points [-]

You care for more than just mircomorts. You also care for not getting brain damage.

Comment author: gjm 03 August 2015 12:36:33PM 1 point [-]

You can measure that in micromorts too, via QALYs.