Some attrition of Add Health respondents occurred over time. Among Black and White respondents, 48.7% completed all four waves, 29.6% completed three waves, 29.31% completed two waves, and 7.5% completed the baseline survey only. Whites were less likely to complete all four waves than Blacks (45.5% versus 55.0%, X2=43.2, df=3, p<0.01). We treated missing data, both attrition and variable missing data, with two approaches. First, we used full-information maximum likelihood imputation in MPLUS software based on the set of covariates described above. Second, we conducted a sensitivity analysis using complete cases (results below), those respondents who completed all four interviews and had complete data on all covariates, only. In these sensitivity analyses, we also incorporated a different set of longitudinal sampling weights that are available on those followed to Wave 4, which adjust the sample to be representative of sample characteristics at baseline.
