Age at first drink reported at Time 1 was subtracted from age reported at Time 2 to create a difference score. Based on difference scores, which ranged from −8 to 15, participants were categorized into one of 3 groups. Per Wittchen et al. (1989), we defined consistent reporting as no more than a 1 year age difference between Time 1 and Time 2 reports. (A total of 525 respondents reported the same age at both time points.) Group 1 consisted of individuals reporting an age at first drink 2 or more years younger at Time 2 than at Time 1 (n=104; 6.1%). Group 3 was comprised of individuals reporting an age at first drink 2 or more years older at Time 2 than at Time 1 (n=520; 30.3%). Group 2 was consistent reporters (n=1,092; 63.6%).
