Not all that long ago, drunk driving was regarded as something anyone could be caught doing. Drunk drivers were not thought of as criminals in the normal sense, and going to jail for a first or even a second offense was unusual.
It's true that drunk drivers are not criminals in the same way that the fellow who knocks over the liquor store is a criminal, or the guy who spends two or three years embezzling $50,000 from the bank. But people generally understand when they've had one too many, and can adjust their behavior accordingly if they want to.
MADD wanted some adjusting as well from the courts' response to drunk driving, and largely succeeded. In recent years, the prospect of going to jail for that offense, even if for only a short time, has considerably increased.
Today, we found out the amazing result.
Is tougher enforcement the only reason for so many more saved lives? No, obviously. Is it part of the reason? You bet.
Moral of story: Society gets the bad behavior it tolerates. When it tolerates less, it gets less. There's a message in their somewhere for the let-them-out-of-jail crowd. Whether they get the message is a different question.