The use of illegal drugs by large numbers of young people in the United States became an issue of considerable concern during the late 1960s and early 1970s. At that time, there were few accurate data available to assess the extent of use on a national basis. In 1975, Lloyd Johnston and Jerald Bach-man of the University of Michigan initiated Monitoring the Future: An Ongoing Study of the Lifestyles and Values of Youth, which was intended to address this lack of information.

One of the major purposes of the study was (and is) to develop an accurate picture of the nature and extent of drug use among young people. An accurate assessment of the amount and extent of illicit drug use in this group is a prerequisite for rational policy making. Reliable and valid data on prevalence are necessary to determine an appropriate...