董事會與審計委員會的兼任對內控缺失的影響：基於美國上市公司的實證研究

Abstract

本研究探討董事會與審計委員會成員之間的兼任對美國上市公司內部控制缺失發生之影響。本文分析在2002年《薩班斯—奧克斯利法案》（Sarbanes-Oxley Act, SOX）通過後，美國上市公司中董事會與審計委員會之間的兼任情形，與內部控制缺失之關聯性。儘管 SOX 推動了多項改革，ICWs 仍為企業與投資人關注的議題。本文基於資源依賴理論與社會網絡理論，探討同時擔任多家公司董事或審計委員的成員，是否能將其公司治理專業知識與風險管理實務帶入所屬公司，從而降低 ICWs 發生的可能性。研究以 2004 至 2022 年 SOX 法案實施後的美國上市公司資料為樣本，發現董事會成員兼任其他公司的董事會成員，特別是在同一產業內的兼任，與 ICWs 呈現顯著負向關聯。此外，若董事擔任其他公司審計委員會成員（尤其是同產業公司），亦顯示對 ICWs 有顯著的負向影響。進一步分析發現，去內控良好的公司兼任，其本公司之 ICWs 發生率亦有顯著下降，顯示存在治理經驗的學習效果；反之，若去內控薄弱公司兼任，則可能帶來污染效果，使本公司 ICWs 增加。此外，我們發現兼任對於內控品質的改善具有正向影響。在方法上，本研究進一步採用負二項迴歸模型與 hurdle 模型，以處理 ICW 計數資料中大量的零值的問題，結果仍具有穩健性。最後，為降低內生性疑慮，本文亦進行內生性檢定，進一步支持兼任行為與 ICWs 之間的負向關係。。此研究拓展了公司治理文獻，提供實證證據說明董事兼任可能有助於強化公司內部控制機制，並指出有意識的董事會結構設計有助於提升監督成效。

This paper examines how overlapping board and audit committee memberships influence the occurrence of internal control deficiencies (ICWs) in publicly traded U.S. firms. This study investigates the relationship between board and audit committee interlocks and internal control weaknesses (ICWs) in U.S.-listed firms following the enactment of the Sarbanes-Oxley Act of 2002 (SOX). Despite SOX’s reforms, ICWs remain a concern for firms and investors. Drawing on resource dependence theory and social network theory, this paper explores whether directors who simultaneously serve on multiple corporate boards or audit committees can transfer governance expertise and risk management practices to their home companies, reducing the likelihood of ICWs. Using data from 2004 to 2022 on U.S.-listed firms following SOX, the findings show that board interlocks, especially those within the same industry, are significantly negatively associated with ICWs. Directors serving on audit committees of other firms, particularly within the same industry, also demonstrate a negative association with ICWs. Additionally, we find that directors are connected to firms with strong internal control systems; their home firms experience a reduction in ICWs, suggesting a positive learning effect. Conversely, interlocks with firms that have poor internal controls are associated with an increase in ICWs, indicating a potential contamination effect. Furthermore, we observe that four distinct types of interlock are positively associated with internal control improvement. The study also employs the negative binomial model and hurdle model to address the excess zeroes in ICW count data, confirming the robustness of these results. Lastly, endogeneity tests further validate the negative association between interlocks and ICWs. This study extends the corporate governance literature by providing empirical insights into how interlocking directorships may strengthen internal control frameworks, suggesting that intentional board structuring could enhance oversight effectiveness.