Steve Stewart-Williams Ph.D.

The Nature-Nurture-Nietzsche Blog

Bike Helmet Laws and the Law of Unintended Consequences

Bicycle helmet laws reduce head injuries - because kids stop riding their bikes

Posted Sep 07, 2015

The economists Sara Markowitz and Pinka Chatterji have an interesting new paper in the journal Health Economics. It's called "Effects of Bicycle Helmet Laws on Children's Injuries," and it addresses the question: Do bike helmet laws reduce head injuries in children?

The short answer is: They do reduce head injuries... but mainly because kids are less likely to bother getting on their bikes if they have to put on a helmet first. And the reduction in bike-related head injuries is almost perfectly matched by an increase in head injuries from other wheeled sports - skateboarding and the like. The law of unintended consequences strikes again!

Here's the abstract:

In recent years, many states and localities in the USA have enacted bicycle helmet laws. We estimate the effects of these laws on injuries requiring emergency department treatment. Using hospital-level panel data and triple difference models, we find helmet laws are associated with reductions in bicycle-related head injuries among children. However, laws also are associated with decreases in non-head cycling injuries, as well as increases in head injuries from other wheeled sports. Thus, the observed reduction in bicycle-related head injuries may be due to reductions in bicycle riding induced by the laws.

​You can read the full article here.

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