Vertical Scales, Deceleration, and Empirical Benchmarks for Growth

Abstract

Empirical growth benchmarks, as introduced by Hill, Bloom, Black, and Lipsey (2008), are a well-known way to contextualize effect sizes in education research. Past work on these benchmarks, both positive and negative, has largely avoided confronting the role of vertical scales, yet technical issues with vertical scales trouble the use of such benchmarks. This article introduces vertical scales and outlines their role in the creation of empirical benchmarks for growth. I then outline three strands of recent vertical scale research that call into question the grounds for relying on these benchmarks. I conclude with recommendations for researchers looking to contextualize observed effects of educational interventions without confounding their effects with vertical scaling artifacts.