Heavy drinking (top panel) and smoking (bottom panel) at Times 1–4 as a function of birth cohort. Item responses for heavy or binge drinking were 1 (never drink), 2 (once), 3 (twice), 4 (3–5 times), 5 (6–9 times), and 6 (10 or more times). Item responses for quantity of smoking were 1 (not at all), 2 (less than 1 cigarette per day), 3 (1–5 cigarettes per day), 4 (about 1/2 pack per day), 5 (about one pack per day), 6 (about 1½ packs per day), and 7 (2 packs or more per day)