Board Diversity and Corporate Investment Efficiency: a Multi-Dimensional Analysis

This study systematically examines the multidimensional impact of board composition diversity on corporate investment efficiency. Drawing upon an annual sample of U.S.-listed companies from 1980 to 2022, a governance diversity index is constructed across four dimensions: gender, nationality, age, and cultural background. This index employs a dual measurement approach combining the Herfindahl–Hirschman Index (HHI) with the exact number of categories, while capital allocation effectiveness is assessed through Tobin’s Q and efficiency metric derived from Data Envelopment Analysis (DEA) method. The study employs a dual fixed-effects model for benchmark testing, subsequently identifying the relative explanatory power of each dimension through a competitive regression framework. Heterogeneity analysis is further conducted based on differences in firm size and growth opportunities. Core findings indicate that nationality and gender diversity significantly enhance investment efficiency, with the positive effect of gender diversity being particularly pronounced in large and high-growth firms. Cultural diversity primarily elevates Tobin’s Q, whereas age dispersion exerts a detrimental impact on operational efficiency. This study contributes by transcending the limitations of single-dimensional research in existing literature. Through a multi-level, synergistic examination and the effective separation of interference between dimensions via competitive design, it reveals the heterogeneous mechanisms and boundary conditions governing the role of diversity. This deepens theoretical understanding of board governance effectiveness, providing actionable empirical evidence and practical insights for listed companies to optimize director selection mechanisms and for regulators to refine diversity governance policies.