Nonlinear Effects of Board Age on Corporate Social Responsibility in Vietnam: The Moderating Role of Product Market Competition

ABSTRACT This study examines whether the relationship between average board age and corporate social responsibility (CSR) is nonlinear and whether product market competition conditions this relationship. Drawing on Upper Echelons Theory and stakeholder, agency, and institutional perspectives, we argue that increasing board age initially supports CSR through greater experience, stakeholder knowledge, and reputational awareness, but eventually constrains it as conservatism and risk aversion become more pronounced. Using 2201 firm‐year observations from 259 Vietnamese listed firms over 2015–2023, we estimate firm‐ and year‐fixed‐effects models and conduct extensive robustness and endogeneity analyses. The results reveal an inverted U ‐shaped relationship between board age and CSR. Because the estimated turning point is below the sample mean, most firms lie on the declining portion of the curve, producing a predominantly negative average association, especially for environmental and governance CSR. Product market competition serves as an important boundary condition: in less competitive industries (higher HHI), the negative effect associated with higher board age is weaker. The findings remain robust across alternative specifications, winsorized data, subgroup analyses, lagged models, fixed‐effects instrumental‐variable estimation, and two‐step system GMM. By integrating a threshold‐based account of board age with an external competitive boundary condition, this study explains when and why board demographics shape responsible corporate behavior in an emerging market.