A Non‐Linear Assessment of the Relationship Between Board Gender Diversity and Firm Performance: Cross‐Country Evidence

ABSTRACT Our study seeks to contribute to the literature by analyzing the effects of board gender diversity (BGD) on firm performance in the UNITED KINGDOM, Germany, France, Italy and Spain by supposing the nonlinearity of this nexus. Also, we aim to determine the thresholds above which BGD exerts a positive impact on firm performance. To achieve this main goal, we employ the Panel Smooth Transition Regression (PSTR) model. The results indicate a single estimated threshold for BGD, suggesting that the effects of women's presence on the board on corporate performance exhibit a nonlinear increase. For Return on Assets (ROA), a threshold is observed at 14.1% women on the board, suggesting that once this proportion is met, the presence of women directors begins to have a more pronounced positive effect on ROA. Similarly, for Tobin's Q , the model identifies a threshold at 15.4% women directors, beyond which their positive influence on performance increases significantly. Below these thresholds, there is a weak or neutral relationship. The results are robust to the change of performance proxies being used and render support for critical mass theory that a minimum level of gender diversity on the board is a prerequisite for BGD to yield positive performance effects. Our findings underscore the significance of gender diversity in the boardroom in enhancing corporate financial performance. Additionally, our investigation highlights the importance of the threshold concept in explaining the divergence in theoretical outcomes toward the sign of impacts between board gender diversity and firm performance. While further analysis is needed for policy implementation, our findings suggest that achieving a critical mass of women on boards is essential to unlock the benefits of gender diversity. Policymakers may consider context‐appropriate strategies—such as mandatory quotas in low‐representation environments or voluntary targets and disclosure‐based incentives in more gender‐progressive settings—to promote balanced board composition.