Estimating Relative Stability in Developmental Research: A Critique of Modern Approaches and a Novel Method

Developmental/life-course (DLC) criminologists often study the age-graded trajectories of traits and behaviors known to correlate with antisocial outcomes. Much of this work has attempted to discern whether traits like impulse control are relatively stable across different portions of the life course. A range of statistical techniques have been used by researchers in attempting to parameterize relative stability. Yet, despite these attempts, much of the evidence remains mixed. The results of the current demonstration indicate that none of the methods typically used by DLC researchers provide a parameter estimate for relative stability. In order to address this oversight, the current study developed a novel methodP(Δ)that can be used to estimate the amount of relative (in)stability that is observed in a longitudinal dataset. The study concluded that although P(Δ) provides a direct estimate of the degree to which relative (in)stability is observed in one's dataset, there are several important points that must be considered by future DLC researchers in order to further develop P(Δ) into a statistic that can be used for inferential analysis. These points are discussed in this article. 51 references (Publisher abstract modified)