Bike Helmet Laws Fail

Two years ago I posted on evidence that called into question the effectiveness of bike helmet laws. A new NBER paper confirms this skepticism:

Using hospital-level panel data and triple difference models. … We consider the effects of the [US bike helmet] laws directly on ['91-'08 US] bicycle related head injuries, bicycle related non-head injuries, and injuries as a result of participating in other wheeled sports (primarily skateboarding, roller skates and scooters). For 5-19 year olds, we find the helmet laws are associated with a 13 percent reduction in bicycle head injuries, but the laws are also associated with a 9 percent reduction in non-head bicycle related injuries and an 11 percent increase in all types of injuries from the wheeled sports. ..

The estimated reduction in head injuries resulting from helmet laws is robust to changes in the definition of the control group, to changes in the type of fixed effects included (state versus hospital), and to changes in the samples of states and hospitals evaluated. … Considering the different offsetting results, we run our preferred specification on injury counts for 1) all head injuries and 2) total (all head and body) injuries arising from cycling and wheeled sports. The net effects of the helmet laws are small and are not statistically different from zero. (more)

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  • Robert Koslover

    Hmm.  You know, the government publishes “recommended daily allowance” (RDA) values for many
    vitamins and minerals.  Most of us are fine with that, pay at least occasional attention to those recommendation, and are free to have
    more or less honest debates about whether the numbers the government sets are best.  Now, how would you like it if, instead, the government insisted that
    under penalty of law, everyone must consume those quantities of vitamins and minerals daily?  That would be quite tyrannical, wouldn’t it?  Well, maybe the same reasoning should apply to many of our current individual-oriented health and safety laws!  Oh, and will somebody please tell NYC Mayor Bloomberg?

  • Anonymous

    By just reading the abstract, bike helmets do not fail, but bike helmet laws fail. I find it more likely that that the bike helmet laws just don’t affect the behaviour of the cyclists that much.

    Here in Finland bike helmets are also mandated by law, but not using a bike helmet doesn’t carry any penalty at all and thus people just don’t care about the law; some people use the helmet and some do not and I suspect that their behaviour would be exactly the same whether the law is in place or not.

  • lukas_bergstrom

    You talk about the effectiveness of bike helmets, but the paper talks about the effectiveness of laws mandating their use. Given moral hazard, we might still conclude that for an individual, wearing a bike helment might be a rational choice. And indeed evidence seems to support that: http://summaries.cochrane.org/CD001855/wearing-a-helmet-dramatically-reduces-the-risk-of-head-and-facial-injuries-for-bicyclists-involved-in-a-crash-even-if-it-involves-a-motor-vehicle

    • http://www.gwern.net/ gwern

      Fulltext: http://www.thecochranelibrary.com/userfiles/ccoch/file/Safety_on_the_road/CD001855.pdf

      It’s a summary of 5 (non-randomized) case-control studies. Doesn’t really seem to address the concerns Hanson has brought up previously. Also has a longer criticism section and appendixes than I used to reading in Cochrane papers… I’m not very familiar with case-control studies, so I need to read it in more detail.

      • Enrique

        Perhaps cyclists with helmets take more risks when riding (e.g. ride faster, take sharper turns, etc.) than they would have without the helmet — this might explain the reduction in head injuries accompanied by offsetting increases in other injuries

  • IMASBA

    Like the other people commenting here it’s my believe that helmet laws are not being followed, explaining the small reduction in head injuries, wearing a bike helmet will significantly reduce the probability of getting a head injury, but then you have to really wear it.

  • Robin Hanson

    I changed the text of the title and first sentence to refer instead to bike helmet laws.

  • Sam Hammon

    For someone who buys into cryonics surely you see the utility in head protection!

  • Siddharth

    I think I’ve become so used to reading this blog that the first time I saw this post, I quickly browsed this page, and I mentally inserted a signalling explanation. The second time I visited, I noticed there wasn’t one, and was confused for a little bit. 

  • newqueuelure

    So is the argument that like shifting from consuming beef to consuming close-substitute pork as beef becomes expensive that people are choosing to consume head injuries from other wheeled sports as cost-inducing regulation (bike helmets) is imposed on bike-related head injuries?

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