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Helmet laws reduce youth cycling

According to a paper presented at the 2nd Conference of the American Society of Health Economics at Duke University on 24 June 2008 by Christopher Carpenter (University of California, Irvine):

Intended and Unintended Effects of Youth Bicycle Helmet Laws

Over the past 15 years, 21 states have adopted laws requiring youths under a certain age (generally 16) to wear a helmet when riding a bicycle. Previous evaluation research finds that these laws significantly reduced youth bicycling fatalities, and the prevailing view is that fatalities fell because helmet use increased. In this paper we confirm that helmet laws reduced fatalities, but we uncover robust evidence of an alternative and unintended mechanism: helmet laws significantly reduced youth bicycling. We find this result in standard two-way fixed effects models of self-reported cycling behaviors, as well as in augmented triple difference (DDD) models that explicitly account for cycling behaviors of youths just above the helmet law age threshold. The reduction in cycling also obtains using independent samples of parental reports of child bicycling behaviors. Our evidence on the effects of helmet laws on helmet use is mixed, though in all cases we find that previous approaches common in the public health literature dramatically overstate the true effects on helmet use. A full cost-benefit analysis of helmet laws should take into account the previously ignored reductions in youth cycling

Tue 24 Jun 2008