Drawing on resource-based and agency theories, this study examines the effects of business concentration and ownership structure on business group performance. On the basis of panel data (2004–2018) from the top 100 Taiwanese business groups investing globally, this study finds an S-shaped relationship between business concentration and business group performance with the interaction of advantages and costs at different levels. Performance increases when there is little business concentration, decreases when there is a moderate amount and increases again when there is a high level of business concentration. In addition, this study hypothesizes that ownership structure has a different moderating effect on this relationship. The family business group has a positive moderating effect; however, outsider direct and manager ownership have no significant moderating role. These findings have important theoretical and managerial implications for business groups.
