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An Air-Bag Wrinkle to Consider

In the SuperFreakonomics chapter on cheap and simple solutions, we wrote:

And seat belts, at about $25 a pop, are one of the most cost-effective lifesaving devices ever invented. In a given year, it costs roughly $500 million to put them in every U.S. vehicle, which yields a rough estimate of $30,000 for every life saved. How does this compare with a far more complex safety feature like air bags? At an annual U.S. price of more than $4 billion, air bags cost about $1.8 million per life saved.*

A reader named Rich Merrill writes in with an interesting comment:

In the early 70’s I was employed at Ford, doing bumpers and air-bag (safety car) testing.? There is another factor that may need to be considered to get an accurate picture of air-bag effectiveness. In order to work well, the occupants must be belted into place.? The air bag doesn’t keep people in place, it just cushions them when they are flailing around at the peak of the impact. And, of course, there are secondary impacts that occur after the air bag has deflated, so belts are?also important for that “post-bag” event.
So, if the current seat belt usage is about 80%, there are 20% of the people riding around with less than optimal air-bag protection.? I’m not sure how you’d measure it, but this would raise the air bag statistics a bit.
Something you might want to put in future editions?
Note: I’m not a big air bag fan and I have no dog in this fight.? I’m a retired engineer (5 years) and left the auto business in 1975.? I agree completely with your comparative “dollars-per-life” analysis.? Simple solutions are just plain hard to “sell.”? Maybe because nobody is making a profit on them? (Pat-downs vs. $canners at airports?)

*See Levitt and Porter, “Sample Selection in the Estimation of Air Bag and Seat Belt Effectiveness,” The Review of Economics and Statistics 83, no. 4 (November 2001).