Working (and studying) day and night: Heterogeneous effects of working on the academic performance of full-time and part-time students

• Analyzes the effect of working on the academic performance of students.
• Focus is on heterogeneous subgroups, particularly full-time and part-time students.
• Effects are identified using student fixed effects and system GMM.
• Increasing work hours negatively affects full-time students’ credit accumulation.
• Little evidence of a detrimental impact of work for part-time students.

A growing number of students are working while in college and to a greater extent. Using nationally representative data from the 1997 National Longitudinal Survey of Youth, I analyze the effect of working on grades and credit completion for undergraduate students in the United States. Strategies to identify the causal relationship between working and academic performance include student-level fixed effects to control for permanent, unobserved characteristics that may affect both work and study intensity, and system GMM models to account for potentially endogenous relationships between working and academic performance that vary over time. I examine the consequences of working for heterogeneous subgroups, with a particular focus on differences between full-time and part-time students. I find no evidence that students’ grades are harmed by marginal work hours, but that full-time students complete fewer credits per term when increasing work.