If it can join the army, buy a gun, vote and run for office (in that order!), then surely the 18-to-20 set should be able to drink:
We tried this before. In the early 1970s, when Congress was still respecting the 21st Amendment, most states lowered their minimum drinking age. That was the time when the Baby Boom cohorts were coming of age and 18-year-old men were subject to the Vietnam draft. The 26th Amendment was adopted in 1970, giving 18 year olds the right to vote. Denying young men who were getting shot up in the war the right to drink when they came home seemed perverse to legislators – especially when those men could vote.
Twenty-nine states lowered their minimum age by 1975. I and a colleague analyzed the effects on highway fatalities, finding that the relevant age group experienced about a 10% increase in states that lowered their age for all beverage types from 21 to 18, compared with states that didn’t change their law. Other research documented this and other indications of increased abuse. President Reagan appointed a commission that documented the problems (with some exaggeration) and ultimately sold Congress on establishing a national minimum.
(Note that we analysts could recite all the theoretical reasons why an age-based prohibition could have perverse effects on health and safety. Those arguments have some truth, but were ultimately trumped by the data. The net effect of lowering the minimum age was to increase alcohol abuse.)
Things have changed since the 1970s, and in some ways it seems likely that the costs of lowering the minimum age would be less now than then. In particular, youthful drunk driving has been curbed by zero tolerance laws, tougher DUI enforcement, and a change in culture that supports having a designated driver. While highway safety remains an important consideration, the greatest acute cost of youthful drinking these days is in its effect on the crime rate. In any event, freedom is still not free in this area.