本研究採用兩階段最小平方法(two-stage least squares，2SLS)檢測外部競爭與公司治理對企業領導結構選擇的影響，並進一步檢視外部競爭對領導結構與公司績效關係的調節效果。研究結果顯示，領導結構的選擇係由內生決定。在快速成長或高度競爭環境下，企業會傾向採用CEO雙重性領導結構，因應快速變動的環境、加强競爭力。當企業具有較大規模董事會，較高董事持股、管理者持股及機構投資人持股，會傾向採用非雙重性領導結構，避免CEO權利過度集中。在控制領導結構選擇的內生性之下，CEO雙重性領導結構與資產報酬率(return on assets，ROA)呈現負向顯著的關係，與Tobin’s q呈現不顯著的關係。值得一提的是，在快速成長與變動的環境、或高度競爭市場中，CEO雙重性領導結構有助於增進公司未來績效。

This study employs a two-stage least squares (2SLS) regression to investigate the influence of external competition and corporate governance on leadership structure chosen, and further examine the moderating effect of external competition on the relationship between leadership structure and firm performance. This study shows that the choice of leadership structure is endogenously determined. In a rapid growth environment or a great market competition, a firm inclines adopting a dual-leadership structure to adjust to changing environments and enhancing competitiveness. A firm with a large board, high director ownership, high managerial ownership, or high institutional shareholdings favors a non-dual leadership structure to avoid CEO power concentration. Controlling the endogeneity of leadership structure, CEO duality is significantly and negatively related to return on assets and insignificantly related to Tobin’s q. Notably, dual-leadership structure enhances future firm value in a rapid growth/dynamic environment or a great competitive market.

Whether a dual leadership structure promotes better firm performance has been one of the most discussed issue in finance and management research. From the perspectives of organizational and management theory, CEO duality creates a centralized leadership structure that grants a considerable amount of decision-making power to the leader. When product market competition and environmental dynamism are high, dual-leadership structure provides flexibility for leaders to make decisions efficiently. According to agency theory, a board of directors is established to protect the rights and interests of stakeholders; only when a board of directors is independent can it effectively oversee the decisions made by a CEO and ensure that his or her decisions accord with the best interests of stakeholders. Controlling for the endogeneity problem, this study indicates that the choice of leadership structure is a nonrandom process which is made accordance with its characteristics, governance structure and external environment. In a rapid growth environment, a firm inclines adopting a dual-leadership structure to adjust to changing environments and enhancing competitiveness. A firm with a large board, high director ownership, high managerial ownership, or high institutional shareholdings favors a non-dual leadership structure. Though CEO duality is significantly and negatively related to return on assets and insignificantly related to Tobin’s q, dual-leadership structure enhances future firm value in a rapid growth / dynamic environment or a great market competition. The relationship between dual-leadership structure and firm performance could be contingent on external competitive environments. CEO duality may generate high agency costs. Financial supervisory agencies worldwide typically encourage firms to separate the role of board chair from that of the CEO. This study indicates that leadership structure chosen is the result of factors such as external environment, ownership structure, and firm characteristics. Particularly, external environment and competitive market are likely to serve as external supervision in mitigating the relationship between dual-leadership structure and firm performance. Therefore, this study serves as a reference for firms to select an appropriate leadership structure and for financial governance agencies in developing related policies.

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