Our analyses assumed that design changes in the NHSDA/NSDUH do not influence prevalences differentially by age or other demographic characteristics. In testing for differences in effect sizes across consecutive survey years differing in design, we found only one case in which this assumption may have been violated. Specifically, there was a significant difference across the 1993 and 1994 surveys in the odds for binge drinking among 12–14 year olds, suggesting that design changes may have led to increased prevalence estimates for this group to a larger degree than for other age groups. This difference was in the opposite direction of the overall trend, which was for reduced rates of binge drinking among 12–14 year olds over time. Therefore, the potential artifact may lead to an underestimation of the decline in binge drinking among 12–14 year olds, but the decline cannot be attributed to confounding due to methodological changes.
