Why is the drinking age requirement 21?

The National Minimum Drinking Age Act was signed into law in July 1984 by U.S. President Ronald Reagan. The law dictated that any state that did not set the age of 21 as the minimum drinking age would lose as much as 10 percent of its federal highway funding. 

However, before this law was signed, years of debates and discussions occurred regarding what an appropriate drinking age should be. Studies found that teenage brains were less likely to be able to handle alcohol consumption without becoming impaired. The thought was that by raising the drinking age, the number of teens drinking and driving would decrease. Before the minimum age drinking law was passed, the most common age group arrested for drunk driving were those between the ages of 16 and 20.

In addition to the scientific conclusions that 21 might be the best minimum drinking age for reducing accidents, there are also historical precedents regarding the age of 21 being akin to the age one reaches adulthood. Centuries ago in England, 21 was the age when one could vote or become a knight.

Mothers Against Drunk Driving has been one of the key proponents in keeping the minimum drinking age at 21. The organization points to a National Traffic Highway Administration report that concludes that the raised drinking age saves roughly 900 lives per year. Since 1982—just before the minimum age law was signed—there has been a more than 60 percent decrease in the number of fatalities in alcohol-related crashes among teens.

Some argue that the drinking age of 21 was never fully thought through and that it should be lowered again. The American Psychological Association asserts that adolescence concludes at about age 19, but maturity is based on an individual's circumstances.  

Some have suggested that if teens complete a 40-hour training course about the risks of consuming alcohol, they should be allowed to drink before reaching age 21. But opponents argue that the health risks for teens and for those with whom they would come into contact would remain.