The main argument for the de facto national drinking age of 21 is that it saves lives. In a recent paper published by the National Bureau of Economic Research, Harvard economist Jeffrey Miron and Yale Law School student Elina Tetelbaum cast doubt on that widely accepted claim.
Overall, Miron and Tetelbaum find, adoption of the higher drinking age is associated with an 8 percent drop in traffic fatalities among 18-to-20-year-olds. But this association is seen mostly in states that raised their drinking ages on their own, prior to the 1984 law that made federal transportation money contingent on a drinking age of 21.
Data from the Monitoring the Future Study, an annual survey of high school students, indicate that the drinking age has, at most, a modest effect on alcohol consumption. A drinking age of 18, Miron and Tetelbaum find, "is associated with an almost 4 percent increase in drinking participation rates, and approximately a 3 percent increase in heavy episodic drinking rates." Again, this association is seen mainly in states that raised their drinking ages before 1984, and it may be partly or entirely due to increased underreporting of newly illegal drinking. Notably, the drop in reported drinking found in the Monitoring the Future survey is not accompanied by a drop in reports of alcohol-related accidents.
The legal drinking age of 21 "fails to have the fatality-reducing effects" commonly attributed to it, Miron and Tetelbaum conclude. While "most of the variation in the [drinking age] occurred in the 1980s," they note, traffic fatality rates have been "decreasing steadily since 1969," probably due to factors such as improved auto safety standards, medical advances, and better driver training.