In the mailed questionnaires, quantity was assessed by the item “On average how many drinks would you have ON EACH DAY THAT YOU HAVE SOME ALCOHOL”, and responses for weekend days were examined. The phase 1 (older cohort) telephone interview question was “Think of the times when you’ve had alcohol during the past 12 months. How many drinks do you typically drink on these days when you had an alcoholic drink?”. For the second (younger cohort) and third (combined cohort) phases of telephone interviews, the question was “In the past 12 months, how many alcoholic drinks would you have on a typical day when you had any alcoholic drinks?”. In the mailed questionnaires and first phase of telephone interviews, the actual number of drinks was recorded. However, for the second and third phases of telephone interviews, participants were given response choices. Subsequently, all responses were coded into the following categories: 1 = zero drinks, 2 = 1–2 drinks, 3 = 3–4 drinks, 4 = 5–6 drinks, 5 = 7–8 drinks, 6 = 9–11 drinks, 7 = 12–15 drinks, 8 = 16–18 drinks, 9 = 19–24 drinks, 10 = 25–30 drinks, 11 = 31 or more drinks.
