Supervision and worker performance: Evidence from a hospital emergency department

Abstract

Research on performance heterogeneity highlights the role of management practices, yet evidence is mixed on whether additional supervisory layers enhance—or slow—operational performance. Leveraging 184,530 patient cases handled by 225 physicians in a Colombian hospital’s Emergency Department (ED) between 2016-2022, we examine how the presence of an ED-medicine specialist supervising generalist physicians affects two key outcomes: patient length-of-stay (speed) and 30-day readmission (quality). Using quasi-random allocation of patients, physicians, and supervisors across shifts, we find that supervision lowers readmission probability by 1.7 percentage points but increases length-of-stay by 7.8 percent. Task characteristics moderate these effects: (a) urgency (low triage) attenuates both the benefits and costs of supervision; (b) ambiguity (no diagnosis at admission) eliminates the quality benefit while magnifying delays; (c) complexity (complex vital signs presentation) shows no differential effect. Mechanism tests suggest the delays stem primarily from increased coordination—more physician hand-offs and specialist consultations—rather than from enhanced monitoring or knowledge transfer. We discuss implications for contingency views of middle management, hierarchy, and job design.