18 as a purchase age, no actual drinking minimum. The best way to prevent unhealthy relationships with alcohol is for parents to expose kids to booze themselves, in moderation- that way it's not some sort of forbidden fruit.
FWIW I was 16 when I first had alcohol and that seems about "right".*
As for the scourge of drunk driving, the obvious solution is to raise the driving age instead. Maybe start introducing learner's permits at 18, and don't issue full licenses until 21. (I would also consider raising the age to serve in the military or to own firearms to 21, along with driving- the privilege of operating deadly machinery is not a right in the way that votin' or boozin' is, and really does need to be only entrusted to people who have demonstrated sufficient maturity. Sorry folks.)
*I would not necessarily oppose a purchase minimum of 16, but it would have to be coupled with raising the driving age for me to support it; and I also don't think it's necessarily a bad thing for teenagers to be able to be exposed to alcohol before they're allowed to buy it themselves.
