Any increase in traffic accidents or fatalities in 18- to 20-year-olds would be offset by a decrease for those 21 and older. Although the United States increased the MLDA to 21 in 1984, its rate of traffic accidents and fatalities in the 1980s decreased less than that of European countries whose legal drinking ages are lower than 21.     Since 1982, two years prior to the Uniform Drinking Age Act establishing an MLDA of 21, a decline of drunk driving fatalities occurred across all age groups and demographic categories, and therefore cannot be reliably attributed to MLDA 21.
Opponents of lowering the MLDA argue that teens have not yet reached an age where they can handle alcohol responsibly, and thus are more likely to harm or even kill themselves and others by drinking prior to 21.
They contend that traffic fatalities decreased when the MLDA increased.
Older youth and adults may furnish alcoholic beverages to minors less frequently, and licensed alcohol outlets may sell to minors less frequently, because of their perceptions that it is illegal, morally wrong, or because they might be caught.
18-year-olds are typically entering a new phase of independence from their parents through college or the workforce, and are more susceptible to binge drinking, risky sexual activity, and other irresponsible behavior due to lack of maturity.
Police are inclined to ignore or under-enforce MLDA 21 because of resource limitations, statutory obstacles, perceptions that punishments are inadequate, and the time and effort required for processing and paperwork.