The majority of the sample exhibited a developmentally limited pattern of externalizing behavior (57.8%), peaking at or before the initial wave of assessment (at age 12), and displaying a steady linear decline thereafter, with no evidence of non-linear change (βintercept = 8.89, p < .001; βlinear = −.48, p < .001; βquadratic = .00, p = .96); we refer to this group as decreasing low externalizing. About one third of the sample (33.4%) showed a longitudinal pattern of change marked by somewhat higher initial levels of externalizing behavior that remained relatively stable before de-escalating in mid-adolescence (βintercept = 13.80, p < .001; βlinear = .27, p = .32; βquadratic = −.07, p = .005); decreasing moderate externalizing. A smaller subset of the sample (8.8%) had even higher initial levels of externalizing behavior that further increased until peaking in mid-adolescence (i.e., at ~17 years of age), then decreased again into young adulthood, though never dipping below early adolescent levels. (βintercept = 16.86, p < .001; βlinear = 1.97, p < .001; βquadratic = −.19, p < .001); that is, a stable
