Debates and Controversies

In spite of the tremendous growth in trajectory research over the past 25 years, the trajectory methodology is not without controversy. Debates and controversies remain a central feature of the literature. This chapter presents an overview of the major controversial issues and provides guidelines and suggestions for moving the research forward with greater clarity and reduced confusion. This chapter also picks up on the discussion of model-building considerations introduced in Chapter 2. Specifically, issues pertaining to (a) statistical criteria for class enumeration; (b) distributional issues, model misspecification, and overextraction of trajectory classes; (c) dependency on antecedents and covariates; and (d) robustness or sensitivity of trajectory solutions in relation to various methodological factors are detailed.