A growing literature documents significant differences in college student outcomes between adjunct and full-time instructors, although less is known regarding the causes of these differences. Many existing studies implicitly treat instructor quality—as measured by an instructor’s effect on student outcomes—as a fixed trait. However, instructor quality itself may be sensitive to employment rank, given that adjunct and full-time instructors work under very different conditions. Understanding mechanisms driving these differences is important for informing policy decisions aimed at improving student outcomes.

Using panel data on first-semester students at public colleges in Arkansas, this paper first establishes that adjuncts have significantly worse student outcomes than full-time counterparts on a number of metrics. Next, the author investigates mechanisms underlying differences in outcomes across instructor rank. The author takes advantage of the panel structure of the data and use an instructor fixed effects approach to provide evidence that within instructors, student outcomes improve when the instructor is full-time, compared to when the instructor is an adjunct.

Results indicates improving student outcomes is about more than just getting better instructors, since instructor quality is not a fixed trait. Rather, factors like an instructor’s conditions of employment and teaching and working environment may affect the outcomes of their students.