There is ample evidence in support of the effectiveness of MLDA-21.
When the age-21 restriction was initiated across states, driver alcohol involvement in fatal traffic crashes declined more significantly among the 18- to 20-year-old population than among drivers aged 21 and older. In 1982, the first year for which alcohol estimates were available in NHTSAs Fatality Analysis Reporting System (FARS), 48% of drivers aged 18 to 20 involved in fatal crashes had some alcohol, compared to 40% for drivers aged 21 and older. In 1989, the year after the last states had enacted their MLDA-21 laws, 34% of drivers aged 18 to 20 involved in fatal crashes had some alcohol, compared to 32% for drivers aged 21 and older. From 1982 to 1989, 18- to 20-year-old drinking drivers in fatal crashes declined 14 percentage points, while drivers aged 21 and older declined by 8 percentage points. In 2006, 26% of the drivers involved in fatal crashes in each age group had some alcohol (NCSA, 2005).
Numerous studies since the National Uniform Drinking Age Act have confirmed associations between raising the MLDA to 21 and reductions in underage alcohol consumption, youthful traffic fatalities, and other harm (e.g., Arnold, 1985; Dang, 2008; Decker, Graitcer, & Schaffner, 1988; O'Malley & Wagenaar, 1991; Ponicki, Gruenewald, & LaScala, 2007; Shults et al., 2001; Toomey et al., 1996; Voas et al., 2003; Wagenaar & Toomey, 2002; Williams et al., 1983; Womble, 1989). Research has revealed a decrease in six types of fatal injuries (including deaths related to car crashes, suicides, homicides, falls, drowning, and alcohol poisoning) for 15- to 24-year-olds following implementation of the MLDA-21 law (NRC/IOM, 2004). NHTSA credits state laws raising the legal drinking age to 21 with preventing approximately 900 traffic deaths annually (NCSA, 2005).
A recent study indicated that the laws making it illegal for youth to possess or purchase alcohol if they are younger than age 21 have reduced the rate of underage drinking drivers in fatal crashes by 11% (Fell et al., 2008). That analysis controlled or accounted for numerous other factors - other drunk driving laws, alcohol consumption, the economy, the culture of the state, and vehicle miles driven in the state - that could have affected underage drinking and driving. Even with all those factors accounted for, the core laws raising the minimum drinking age to 21 still resulted in a substantial reduction in youth traffic fatalities. This confirms the findings of prior research but has a stronger design than many earlier studies.
NHTSA estimates that minimum drinking age laws have prevented 26,333 traffic deaths since 1975. This estimate represents people of all ages who otherwise would have been involved in a fatal crash involving 18- to 20-year-old alcohol-impaired drivers (Figure 1). This number would be higher if the number of lives saved through the prevention of other underage drinking deaths (e.g. suicides, homicides, unintentional injury deaths) were included.