Nguyen Thi Thu Thuy

Type of the article: Research Article

Abstract
Ownership concentration (OC) remains a subject of debate in emerging markets, particularly under heterogeneous institutional conditions and firm characteristics. This study examines how ownership concentration affects firm performance (FP) in Vietnam, while also analyzing the roles of firm size and subnational institutional quality in shaping this relationship. Using a balanced panel dataset of 425 non-financial listed companies over the period 2015–2024, the analysis applies the two-step system GMM approach to mitigate potential endogeneity concerns, with institutional quality proxied by the Provincial Competitiveness Index (PCI). The findings indicate that ownership concentration exerts a positive and economically meaningful effect on firm performance. This effect is substantially strengthened by both firm size and institutional quality, indicating pronounced heterogeneity across firms and regions. Specifically, the performance-enhancing role of ownership concentration is more evident in larger firms and in provinces with stronger institutional environments. In addition, the three-way interaction among ownership concentration, firm size, and institutional quality is significant, suggesting that these factors jointly reinforce the effectiveness of ownership concentration. The findings show that the performance implications of ownership concentration are shaped by the interaction between local institutional conditions and firm-specific factors.