A new study shows a decrease in the number of teens drinking and driving. This is a great article written by someone who actually understood the study! Not only do they explain the current statistics, but it compares them to the numbers from 1 and 20 years ago. The author describes the method as a national survey. While they do not go in depth on the method there is a link provided, for those interested, to investigate further.
It seems the reason for the decline is the stricter laws that are being enforced throughout the country. Of the 41 states surveyed "the percentage of students who reported drinking and driving in the previous 30 days ranged from a low of 4.6 percent in Utah to a high of 14.5 percent in North Dakota." Seems like a pretty intensive study to me.