How Do "Point Oh-Eight" (.08) BAC Laws Work?

Abstract Over the past two decades, states have toughened their adult drunk driving laws by setting the legal blood alcohol content (BAC) threshold at .08, down from .10. Although several studies have shown that these laws have been effective at reducing alcohol-related traffic fatalities, there is very little evidence on the underlying behavioral mechanisms through which .08 BAC laws achieve the fatality reductions. We estimate reduced form models of the effects of .08 BAC laws on a wide range of self-reported alcohol-related risk behaviors using large samples from the Behavioral Risk Factor Surveillance System (BRFSS) and the National Surveys on Drug Use and Health (NSDUH) from 1999-2003 – a period when 32 states’ .08 BAC laws went into effect. Models with state and year fixed effects provide no evidence that .08 BAC laws reduced alcohol-involved driving, and we similarly find no effects on drinking participation or the likelihood of binge drinking. We do find robust evidence, however, that .08 BAC laws reduced past month alcohol consumption among moderate drinking males by about five percent. These reductions are larger for older, college educated, and married men. Taken together with results from previous research on other drunk driving interventions, our findings confirm a general deterrence effect and suggest that tougher drunk driving laws work primarily by reducing alcohol consumption.