An unconditional means model with random intercepts was fit to the trajectories of externalizing problems and showed considerable within-person (σ2ε = 61.26, SD = 7.83) and between-person (σ20 = 56.33, SD = 7.51) variance, suggesting that the average person varies over time, and that the cross-time means of externalizing problems differ between individuals.1 Moreover, the intraclass correlation was ρ = .48, suggesting that about half of the variability in externalizing problems is between individuals, and that externalizing problems have a high residual autocorrelation over time.
