ABSTRACT
It should be kept in mind that throughout this chapter, when we refer to friends' use of substances, we are really reporting respondents' perceptions of such use. We asked respondents (in some, but not all, of our questionnaire forms) to estimate how many of their friends did each of the following: smoke cigarettes, smoke marijuana, take cocaine, use alcohol, or "get drunk at least once a week." For each substance use dimension, the response scale was "none, a few, some, most, all." As we show in this section, distributions of responses to these simple and straightforward questions correspond consistently with the age-related changes in self-reported drug use that we detailed in our earlier volume (Bachman et al., 1997). Thus, for example, just as proportions of marijuana users declined as young adult cohorts moved from age 18 through age 32, so also did the proportions of reported friends using marijuana decline. Later in this chapter we show also that, at the individual level of analysis, these ratings of friends' use correlate highly with self-reported use. Both sorts of findings provide evidence of the construct validity of these measures of friends' use.
