Methods for studying union effects: a review and comparative analysis of empirical Industrial Relations literature

This paper reviews methodological developments in Industrial Relations (IR) research on union effects from 1990 to 2023, based on 511 studies in six leading IR journals in the United States, the United Kingdom, Canada, and Australia. We find that institutional contexts shape methodological choices over time and note a general shift from descriptive analyses to advanced quantitative approaches, such as fixed effects, instrumental variables, and quasi‐experimental designs. At the same time, however, qualitative and mixed methods remain central to the field. The paper further shows that research agendas have expanded from focusing on wages, collective bargaining, and workplace HR policies to include political and societal outcomes. Finally, we situate IR studies of union effects relative to adjacent disciplines: economics, sociology, political science, psychology, and management. Bibliometric analysis reveals close ties between IR and economics, as well as shared research interests with sociology and political science. The findings suggest IR has increased its methodological sophistication and maintained a pluralist identity – with both features informed by changing research priorities, national institutions, and ongoing dialogue with adjacent disciplines.