Group-Based Trajectory Modeling (Nearly) Two Decades Later

Nearly two decades have passed since the publication of Age, Criminal Careers, and Population Heterogeneity: Specication and Estimation of a Nonparametric Mixed Poisson Model by Nagin and Land (1993). In that article Nagin and Land laid out a statistical method that has come to be called group-based trajectory modeling. The principle objective of the paper was to address issues related to the hot topic of the time--the criminal career debate--not to lay out a new statistical methodology.