Reported alcohol use in the previous month among high school seniors appears to have decreased from 1975 through 1996. NIDA changed the wording of the alcohol use question in 1993. The new question required reports of heavier use to qualify as having used alcohol in the last year, however the exact wording of the question is not given on the NIDA web site. For 1993 (when both questions were asked), the new question results in 2.4% fewer students being classified into the category of "Having used alcohol in the last year" than did the old question. If we assume that the differences observed between the two alcohol use questions in 1993 would have been around the same size in 1994 through 1996, then adding that difference to the percent obtained from using the new alcohol use question should approximate the findings if the old alcohol use question had been used. This difference is represented on the graph by the white bars at the top of each alcohol bar. In the 1970s around 70% of high seniors admitted using alcohol during the past month, whereas in the 1990s this percentage dropped to around 50% of seniors who admitted using alcohol during the past month. Any illicit drug use during the past month dropped from a high of nearly 40% in the late 1970s to a low of around 15% in 1992 and has increased to almost 25% in 1996. Marijuana use during the past month dropped from a high of over 35% in the late 1970s to a low of around 10% in 1992 and has increased to over 20% in 1996. It appears that the majority of students who reported using any illicit drug during the past month, also reported using marijuana during the last month. This effect was consistent across each year of the survey.

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