Motorcycle helmet laws and motorcyclist fatalities

We employ panel data over a 22-year period to study the impact of state law s mandating helmet use by motorcyclists. We find that helmet laws are assoc iated with an average 29-33% decrease in per capita motorcyclist fatalities . However, since voluntary helmet wearing rates are higher in harsher clima tes, the efficacy of helmet laws varies directly with the warmth of a state 's climate. Repeal of helmet laws in the 1970s and subsequent re-adoption i n the late 1980s and early 1990s have had roughly symmetrical effects on fa talities. Alcohol consumption and the number of police available to enforce traffic laws also significantly effect motorcyclist fatalities.