An empirical test of the offset hypothesis

I exploit cross-province and time-series variation in Canadian mandatory se at belt legislation to empirically test the offset hypothesis. The results of this study offer modest evidence of the existence of offsetting behavior by drivers. Specifically, increased use of seat belts by drivers after the enactment of seat belt legislation should have led to a 29 percent decreas e in driver fatalities. However, econometric estimates indicate that the in troduction of seat belt legislation is significantly correlated with only a 21 percent decline in driver fatalities. Furthermore, the use of legislati ve and nonlegislative factors to control for the effects of independent det erminants of traffic fatalities is critical, as the omission of these effec ts implies that seat belt laws are associated with roughly a 32 percent dec rease in driver deaths, thus implying an absence of significant offsetting behavior.