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The difference between “theoretically possible” and “important”

Academics, myself included, love coming up with counterintuitive arguments that change the way people see the world. The media probably loves to publish such articles even more than the academics like to find them.

Sometimes, though, these same academics/media do a big disservice by raising issues that are theoretically possible, but not at all important in reality.

A great example appears in this article in Time magazine about how maybe seat belts don’t save lives because drivers become more reckless when belted because they feel safer. This effect could reduce, or even reverse the safety benefits of seat belts.

The theory is sensible. When I am unbelted, I am at greater risk for injury, so I may drive more cautiously. In economics, this idea is attributed to my friend and colleague Sam “Seatbelt Sammy” Peltzman in the 1970s. Economists call this tendency the “Peltzman Effect.”

In practice, though, the evidence could not be clearer that seat belts are an incredibly cost effective way of saving lives. (See for instance, this study of mine and the citations therein.) Whatever small offsetting impact that more reckless driving due to seat belts may have, it is trivial compared to the benefits of wearing a seat belt. Articles like the one in Time Magazine encourage people to come to completely the wrong conclusion on this question.

If, however, I’m wrong and compensating behavior on the part of drivers really does undo or reverse the benefits of seat belts, there is an easy public policy solution: the government should mandate the installation of a razor sharp knife on every steering wheel aimed directly at the heart of the driver. Just think how carefully we would all drive then.