sample (ascertained as adolescents through the school system) that contributed the 17- and 18-year olds at Wave 1. Another possibility is that the computerized administration of the CIDI-SAM at Wave 2 may have led to slightly different prevalence estimates than those elicited by the paper and pencil interview format at Wave 1. Finally, being assessed for a second time may have resulted in lower endorsement of behavior. Although we are not able to disentangle these contributions to the lower prevalence estimates for 17- and 18-year olds at Wave 2, it is apparent that at older ages the prevalence rates for Wave 2 are in line with what would be expected projecting forward from Wave 1.
