The data reported in Chapter III clearly demonstrate the changes in youth drinking, drinking and driving, and other related behaviors since 1982.
As Chapter IV shows, the causes of this decrease are not nearly as well documented or understood.
Three influences are well-documented and well-understood: population changes, drinking age increases, and zero tolerance laws. Influences from the remaining factors - youth programs, other drunk driving measures, and factors completely apart from driving or drinking - can only be inferred. While MLDA 21 and zero tolerance laws clearly had some effect, they equally clearly did not cause the entire decrease. Canada's decrease was identical, with no drinking age changes, and states whose drinking age was 21 before 1982 also shared in the decrease. Zero tolerance laws were implemented only in the 1990s, after most of the youth drinking and driving decrease had occurred.
The influence of drinking and driving measures directed at all drivers, not just youth, seems clear, both from the data of Chapter IVD and from common sense. However, youth drinking and driving decreased substantially more. Some of the difference may be due to the youth-directed measures of drinking age increases and zero tolerance laws. Another possibility is that some general measures may have a stronger effect on youth than on older drivers. For example, drinking and driving enforcement publicity may prompt parents to exert more control over their young drivers. Or the threat of a driver's license suspension may affect youth more than older drivers.
The effects of programs directed at youth are the most uncertain. These programs touched virtually all youth to some degree, through the schools, the media, and activities in their community. There is abundant anecdotal evidence that specific programs had some impact: students said they were affected by assembly programs featuring drunk driving victims or by "mock crash" events; no youth alcohol-related crashes occurred on Project Graduation weekends; virtually every student knows the dangers of drinking and driving. But there is little or no proof of any direct effect on youth drinking and driving. On the other hand, their cumulative effect may have been crucial in producing the youth attitude, behavior, and crash changes over the past 20 years. We simply do not know.
Lacking firm data and firm conclusions, it's difficult to make definitive recommendations. Those that follow come from the authors' experience and best judgment as well as the information presented in this report.
Something worked spectacularly well in reducing youth drinking and driving. Some causes are known; some are not. But none of the broad activities directed at youth drinking and driving over the past 20 years has been proven to be useless. So, carry on: continue enforcing the laws, continue the programs directed at youth, continue measures against all drinking and driving.
Both MLDA 21 and zero tolerance laws are poorly enforced, for several reasons: their enforcement may not be a priority; police may lack the necessary resources; enforcement procedures may pose obstacles; the laws themselves may have loopholes or unfortunate provisions. If enforcement improves, youth drinking and driving is likely to drop further.
Youth cultures change quickly. Programs and methods that affected last year's youth may be irrelevant to next year's. Continue the research, the experimentation, and the programs; inform, motivate, involve, and affect youth; reduce drinking and drinking and driving even further.