Abstract
The authors employ panel data over a 22-year period to study the impact of state laws mandating helmet use by motorcyclists. The authors find that helmet laws are associated with an average 29-33% decrease in per capita motorcyclist fatalities. However, since voluntary helmet wearing rates are higher in harsher climates, the efficacy of helmet laws varies with the warmth of a state's climate. Repeal of helmet laws in the 1970s and subsequent in the late 1980s and early 1990s have had roughly symmetrical effects on fatalities. Alcohol consumption and the number of police available to enforce traffic laws also significantly effect motorcyclist fatalities. (A)