Mapping the Contradictions: A Systematic Review of the Relationships between Customer Concentration and Financial Performance

HRMARS - Amid escalating global supply chain disruptions, customer concentration (CC) has become a critical variable affecting firm financial performance (FP). This study systematically reviews 79 peer-reviewed articles published between 1995 and 2025 from Scopus and Web of Science, applying bibliometric tools (CiteSpace, VOSviewer) to map the intellectual structure and thematic evolution of the CC–FP relationship. The findings reveal three distinct patterns: (1) CC may enhance FP through economies of scale and strategic partnerships; (2) excessive concentration increases financial risk and volatility; and (3) a growing number of studies report nonlinear effects, including U-shaped (FP first declines, then improves) and inverted U-shaped relationships (FP peaks at moderate CC levels). Emerging themes include digital transformation, ESG, and green innovation. The review addresses a significant gap in integrating fragmented empirical evidence and offers guidance for future research on moderating mechanisms and industry-specific heterogeneity. Practically, the findings urge managers to balance efficiency with risk diversification in customer portfolios, especially in dynamic or ESG-sensitive sectors. Future research should examine how digital and green capabilities shape the CC and FP nexus under different institutional contexts.