Purpose Prevailing accounts portray trade unions as inherent obstacles to HR outsourcing, explaining instances of acceptance mainly through globalization or cost-efficiency logics. Integrating institutional theory and HR architecture, this study moves beyond such universalistic explanations by examining how the relationship between trade union influence and HR outsourcing in different service areas varies between three cultural clusters, thereby advancing understanding of cross-regional variation in employment systems. Design/methodology/approach Leveraging data from the 2021 Cranet survey of 2,635 organizations in the Anglo, Germanic, and Nordic cultural clusters, this study uses correlation and multiple regression analyses to test the relationship between trade union influence and outsourcing across eight HR service areas, and moderation analysis with the PROCESS module in SPSS to examine the moderating effect of cultural cluster, based on the GLOBE classification. Findings The results show that trade union influence drives the outsourcing of HR services such as payroll, training, outplacement, recruitment, selection, and routine queries in the Anglo and Germanic clusters, whereas in the Nordic cluster, the relationship is generally weak or statistically insignificant. These findings suggest that the impact of trade unions on HR outsourcing depends on institutional contexts and the way HR practices are structured within organizations, with union influence facilitating outsourcing in the flexible Anglo systems and the formalized Germanic systems, while the collaborative, consensus-oriented HR arrangements in the Nordic cluster appear to buffer this relationship. Originality/value This study is the first to show that HR outsourcing is both strategically differentiated and institutionally embedded, rather than a universal or purely efficiency-driven practice. By integrating institutional theory with HR architecture in a cross-regional cultural context, it demonstrates that the classification of HR services as “core” or “non-core” is culturally constructed, that HR architectural differentiation itself is shaped by institutional pressures, and that trade union influence shapes outsourcing through locally embedded legitimacy judgments. These insights refine outsourcing theory, challenge Anglo-centric universalistic assumptions, and also provide guidance for multinational firms seeking to align HR strategies with diverse institutional contexts.
Kazemi et al. (Mon,) studied this question.