While alcohol remains the No. 1 health risk to young people, research on youth drinking and driving has shown some positive news in the last two decades. Between 1982 and 1998, the population-weighted rate of drinking drivers younger than 21 in fatal crashes declined by an amazing 59 percent. The National Highway Traffic Safety Administration gives most of the credit to the minimum legal drinking age law enacted by Congress in 1984. The law saves more than 900 lives a year.

Despite this good news, skeptics and prevention opponents continually attack the minimum drinking age. They point to the ease with which teens still obtain alcohol, the drunken parties in fraternity houses, the teen keg parties in the homes of absent parents and the deaths of prom night drivers.

While the minimum drinking age law is often violated, its shortcomings are not within the law itself but rather its enforcement. There's limited interest among adults in seeing the law fully enforced. This lack of concern creates an environment in which merchants, who primarily focus on sales, are permitted to be sloppy in their efforts to prevent sales to minors. Taking time to check IDs can be a nuisance for managers and clerks, a diversion from the key activity of making a living. House parties hosted by a young adult are another major source of alcohol for minors. Some communities recognize this threat to public health and safety and have approved "social host" laws and enforcement, using hefty civil fines to deter adults from allowing minors to drink at their parties. But most communities just look the other way.

Studies show that when police have the resources and public support, they can substantially reduce minors' access to alcohol. When owners and managers of alcohol outlets are convinced that the drinking age is being actively enforced, they tighten up on age checking and substantially reduce alcohol availability to youths. Cracking down on underage drinking at house parties has borne similar successes.

In many communities, however, store owners and party hosts correctly perceive that the minimum drinking age law is not being actively enforced, and so they furnish alcohol to minors with little concern about getting into trouble. Why this low priority, when we know that alcohol is the greatest health and safety threat to teens?

Few parents welcome the sight of a drunken teenager, but, particularly with boys, adults treat this as an inevitable right of passage, a temporary, ultimately unimportant occurrence on the way to adulthood. Even when parents are disturbed that their teen is drinking, they feel powerless to control the problem because their son or daughter has access to alcohol from peers, parties and illegal sales.

The 1984 minimum drinking age law speaks to that problem. It's a very family-oriented, conservative public policy. As written, the law is intended to cut off sources of alcohol external to the family home. That seeks to ensure that parents have the strongest role in decisions regarding their children's alcohol use. When the minimum drinking age is not enforced, parents' authority over their households and their children is undermined.

Whether by failure to take the problem seriously or out of frustration, society tends to dismiss underage drinking. It's even the source of humor in popular culture, just as impaired driving used to be in the 1970s – until the advent of citizen activist groups such as Mothers Against Drunk Driving. We need a new wave of activism focused on underage drinking to motivate parents to support minimum drinking age enforcement in their communities. Once that happens, it will become a priority for police and policy-makers.

Parents need to be educated on the data about how underage drinking leads to death,  injuries, school problems, teen pregnancy, sexual assault on teen girls, juvenile crime, damage to the developing adolescent brain and the onset of adult drinking problems. This knowledge can be wielded by communities to demand the reduction of alcohol availability to youths. That, in turn, will empower parents to take control of their teenagers' drinking decisions. Despite the belief by many parents that teen drinking is beyond their control, they have the power to protect their sons and daughters through strong support for minimum drinking age enforcement.

Robert Voas, a senior research scientist for PIRE Public Services Research Institute, has studied alcohol-related problems and solutions for more than 30 years.