In these analyses, we calculated trajectories of aggression as determined by individuals’ relative positions in the distributions of aggression scores at each wave. This method of trajectory analysis differs from the latent class trajectory methods that are now applied commonly in research on the development of aggression from childhood to adolescence [e.g., Broidy et al., 2003; NICHD, 2004]. However, such latent class methods rely on repeated identical absolute measures to indicate aggression—e.g., yearly frequency counts of a specific aggressive act. Within our life-course developmental perspective spanning childhood through adulthood, this method of analysis is less appropriate because the nature, meaning, and measurement of aggressive acts vary significantly over time [Boxer et al., 2005; Tremblay, 2000].
