Chou et al. (2013)研究指出，若公司董事同時有兼任其他公司董事的情形，其在外兼任之公司數目越多，對原公司價值有越顯著之正向影響。Bouwman (2009)研究亦指出，當公司與其他公司之董事有重疊的情形時，其公司政策也會受到董事重疊（director overlap）之公司的影響，如公司的董事會規模、執行長薪酬、董事薪酬…等治理政策，表示在公司之前存在著社會網路 (social network)，影響公司間政策的制定及績效。
　　本文以美國不動產投資信託（REITs）產業為研究對象，探討此一受到政府法規高度管制的產業，在公司董事同時兼任其他公司董事的情形下，是否對公司治理政策及績效造成相當程度的影響。研究結果發現，董事重疊之現象會影響不動產投資信託產業之公司治理政策，且對於公司經營績效則也有顯著之影響。我們認為，對於美國REITs產業而言，在公司治理政策的制定上，依然會受到社會網絡 (social network)的影響。而同樣地，相較於一般產業，美國不動產投資信託（REITs）並不因其產業性質特殊而有不同結果，對公司經營績效而言，同樣有顯著的正向影響，即使在透過資產類型的不同加以控制後，依然有相同的結果。

Chou et al. (2013) have indicated that when the number of simultaneous directorships held by a person increases, the effects of those simultaneous directorships on the director’s original firm are significantly positive. Additionally, Bouwman (2009) has noted that the phenomenon of director overlap—meaning that a firm’s directors also hold directorships at other firms—affects firm policies such as board size, CEO and director salaries, and other governance policies.
　　Our target industry is U.S. real estate investment trusts (REITs), a highly regulated industry. We want to discuss whether the phenomenon of director overlap will exert considerable influence on corporate governance policies and performance. Our study finds that the phenomenon of director overlap will affect a REIT’s corporate governance policies and significantly affect its operating performance. We believe that the U.S. REIT industry remains affected by social networks in establishing corporate governance policies. Moreover, as in other industries, the operating performance of U.S. REITs is significantly impacted by social networks.

國立中山大學研究生學位論文審定書 i
摘要 ii
Abstract iii
1. Introduction 1
2. Literature Review 6
2.1 Corporate governance policies and director overlap 6
2.2 Director overlap and corporate performance 8
3. Hypotheses Establishment 10
4. Methodology and Data 13
4.1 Data description 13
4.2 Empirical models and variables description 14
4.2.1 Hypothesis 1: relation between policies and directorships 15
4.2.2 Hypothesis 2: how directorships affect elections 17
4.2.3 Hypothesis 3: do directorships improve performance? 19
5. Empirical Results 22
5.1 Relationship between director overlap and policies 22
5.2 Relationship between the policy gaps and director election 23
5.3 Relationship between overlapping directorships and firm performance 24
6. Conclusion 27
Reference 36

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