A new study from the National Bureau of Economic Research by Pinka Chatterji and Sara Markowitz indicates a way that bicycle helmet laws may be creating less bicycle-related head injuries: discouraging getting on the bike in the first place. From the summary:
In recent years, many states and localities have enacted bicycle helmet laws. We examine direct and indirect effects of these laws on injuries. 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.
Read Nick Gillespie's Reason classic on the pathologies of "Child-Proofing the World."
Helmet tip for study pointer: Jonathan Grubb.