Here is an interesting article on drinking laws in the US.
web.syr.edu/~su4rally/age_history.html
Apparently, prior to 1984, each state set its own drinking age. Some states had lower drinking ages. Teenagers from bordering states would drive to those states and drink, then drive home. This caused accidents.
It was determined that 5% of the alcohol related deaths were caused by teenagers, so it was thought that if the drinking age was raised that would help.
No one knows if this worked. THere are better seat belt laws, education about drunk driving, etc. So, although drunk driving accidents have gone done, we can’t be certain that this is because of raising the age.
this is from the article:
***One problem with these figures is that in the mid 80’s seat belt laws were created. That means that there were less fatal car accidents overall, so the number of alcohol related traffic fatalities had to go down. The only two sources for tracking the number of people driving drunk are arrest reports and autopsy reports. Limiting the number of fatalities makes the drunk driving figures go down, even if the number of drunk drivers remains the same. ***