time year by year up to their present age, asking if their drinking patterns had changed and, if so, asked them to document the new pattern. If necessary, the interviewers would use other memory prompts from the information previously recorded on the calendar to ‘cue’ the respondent into the relevant ‘memory files’. The test–retest reliability of our assessments of average monthly alcohol consumption (calculated as the product of the average number of days per month of drinking and the average number of drinks per day when drinking) has been presented in detail elsewhere (Kendler et al. 2008, Fig. 2) and exceeded +0.85 for the time period considered here. The key dependent variable for our analyses was the maximum reported yearly alcohol use for each of the age periods examined.
