Drunk driving among American teenagers has sharply declined over the past two decades, according to the Centers For Disease Control.

A study released Tuesday revealed that the number of high-school students aged 16 and above who self-reported driving drunk fell by 54 percent. The reasons behind the plunge were both predictable and surprising.

First, the CDC concluded prevention efforts had made an impact. The second major reason for the drop was simply that, sober or not, teens are not driving as much.

Twenty-two percent of high-school seniors said they did not drive during an average week, a figure that has jumped 33 percent since 2000, according to the survey.

Part of the reason for that is because many states have implemented graduated driver-licensing programs that extend the learner's permit period and restrict driving at high-risk times, such as night. Another reason: "Teens are especially sensitive to increases in gasoline prices and declines in economic conditions," the report concluded.

Earlier this year, Reuters reported that driving miles were significantly down among younger Americans, and in particular, 26 percent of Generation Y members didn't even hold a driver's license.

Even as the numbers track downward, teen drinking and driving remains a worrisome topic. Although self-reported incidents have declined, 1 in 10 students reported drinking and driving within the past 30 days. Among teenagers involved in fatal accidents in 2010, the latest year for which data was available, 20 percent had alcohol in their blood.

More than 2,200 U.S. teenagers were killed in car crashes that year, and approximately 800 were alcohol-related, according to the CDC. Auto accidents remain the No. 1 cause of death for Americans between the ages of 13 and 19.

"Their number of crashes and crash deaths are disproportionately high," said the Insurance Institute for Highway Safety, noting the fatal crash rate per mile for 16 to 19-year-olds is nearly three times the rate than for drivers ages 20 and over.

Results in the CDC survey varied widely on a state-by-state basis.

Utah reported the lowest overall rate, with only 4.6 percent self-reporting incidents of drinking-and-driving within the past 30 days, followed by Indiana (6.5 percent) and New York (6.5 percent).

North Dakota reported the highest overall rate, with 14.5 percent of respondents saying they drove drunk in the past 30 days, followed by Wyoming (14.3 percent) and Iowa (13.6 percent).