在公司治理中廣被探討的理論有代理理論與管家理論，而兩者理論在於董事長兼任總經理對於企業績效之影響有著不一樣的看法，代理理論認為二職合一會使得代理問題更容易發生，進而產生代理成本，降低企業績效；而管家理論則認為兩職合一的管理方式可使總經理能加速公司決策，以極大化企業利益為使命，故會使得公司績效上升。
本研究採用縱橫資料型態(panel data)來探討台灣上市家族企業中董事長是否兼任總經理及家族持股對企業績效之影響，並進一步透過家族持股來作為交互作用，檢視是否強化或弱化企業績效與董事長兼任總經理之間聯結，期許能對研究家族企業之領域提供管理建議。實證結果顯示，不論是會計績效指標ROA或者市場績效指標Tobin’s Q，皆顯示董事長兼任總經理會對企業績效有顯著正向影響，表示建議家族企業可以以二職合一的方式管理公司，而關於家族持股部分，會計指標ROE、ROA皆為正向相關，代表家族持股比率越高，企業績效會越好，不過兩者之交互作用項卻會弱化企業績效與董事長兼任總經理之間聯結，故會建議有兼任之家族企業不宜持股過多，以避免抵消總經理雙元 、家族持股比率與企業績效間之正向影響。

Using the competing agency theory and stewardship theory perspectives, this study empirically examines the relationship between CEO duality and firm performance in Taiwanese listed family controlled firms. According to the agency theory, agency problem will happen more easily when the CEO is the chairman simultaneously. However, based on the stewardship theory, when the CEO is the chairman, CEO can make the decisions more efficiently.
This study uses panel data to examine the relationship between CEO duality and firm performance. And use family ownership to test the moderating effect. Empirical results show that when the CEO is the chairman, it positively affects the company’s ROA and Tobin’s Q. Family ownership positively affects ROE and ROA. Contributions, limitations, practical implications, and directions for future research are discussed.

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