How and Why Do Adjunct Instructors Affect Students’ Academic Outcomes? Evidence From Two-Year and Four-Year Colleges

By:  Florence Xiaotao Ran & Di Xu | January 2017

Based on a dataset on two- and four-year college students and instructors from an anonymous state that includes detailed instructor employment information, this paper classifies faculty into four types—tenured instructors, tenure-track instructors, long-term adjuncts, and short-term adjuncts—to examine whether adjunct faculty have different impacts on student academic outcomes than tenure-track and tenured faculty. The authors use two empirical strategies—a two-way fixed effects model and an instrumental variable approach—to examine how initial exposure to a field of study with different types of instructors influences both contemporaneous and subsequent course performance in both two- and four-year colleges, as well as the extent to which the estimated differences on student outcomes may be explainable by observable instructor academic and employment characteristics. The authors’ results suggest that adjuncts have positive impacts on introductory course grades but negative impacts on subsequent course enrollment and performance. Such negative impacts are stronger among supplemental adjuncts hired temporarily than among adjuncts with long-term employment contracts with the college. The estimated differences among instructors can be largely explained by key instructor demographic and employment characteristics, including highest degree attained, whether employed full-time in the college, and whether had previous work experience in non-teaching positions.