رابطه پویا بین دوگانگی مدیر عامل و عملکرد شرکت: نقش مستقل استقلال هیئت مدیره  The dynamic relationship between CEO duality and firm performance: The moderating role of board  independence

1. Introduction CEO duality and its impact on firm performance represents one of the most contentious issues in both academia and business (Dalton, Hitt, Certo, & Dalton, 2007; Finkelstein, Hambrick, & Cannella, 2009). In recent years, especially since the passage of the Sarbanes-Oxley Act of 2002, agency arguments and empirical evidence on the negative performance impact of duality (Fama & Jensen, 1983; Jensen, 1993) have led to calls for abolishing the combined leadership structure. Activist shareholders of various firms (e.g., News Corp, JP Morgan Chase, and Goldman Sachs) have campaigned against CEO duality by initiating proposals requiring its outright prohibition. Conversely, some firms (e.g., Chevron Corporation 2012) have provided arguments to support the value-enhancing attribute of the unity of leadership that duality engenders. Thus, determining whether CEO duality ultimately enhances firm performance is an increasingly important question for corporations, business practitioners and academics. ions, business practitioners and academics. Two primary theoretical perspectives dominate the research on duality’s performance effects. Agency theory argues that duality increases the power the CEO has over the board, hindering the independence between the board and management that is necessary to check managerial entrenchment (Jensen & Meckling, 1979; Fama & Jensen, 1983), resulting in negative performance effects (Jensen, 1993). In contrast, management and organizational scholars, relying on stewardship theory (Donaldson & Davis, 1991) and resource dependence theory (Pfeffer & Salancik, 1978), argue that duality promotes more focused and flexible leadership which facilitates organizational effectiveness in a potentially dynamic business environment (Finkelstein & D’Aveni, 1994; Dahya, Lonie, & Power, 1996). The empirical literature investigating duality’s impact on firm performance yields mixed results. Evidence from the 31 studies reviewed in Dalton, Daily, Ellstrand, and Johnson (1998) is inconclusive, ranging from positive to negative to statistically insignificant relationships (e.g., Daily & Dalton, 1994; Faleye, 2007). Because a board’s choice of leadership structure might be endogenous (Faleye, 2007; Hermalin & Weisbach, 1998; Raheja, 2005), the ambiguous results on the relationship between duality and firm performance are often deemed a consequence of endogeneity problems (Harrison, Torres, & Kukalis, 1988; Adams, Almeida, & Ferreira, 2005) that make it difficult to identify a causal relationship between the two. Recent research (Iyengar & Zampelli, 2009) investigates this possibility and documents that studies which treat CEO duality as exogenous do not suffer from selection bias. Consistent with this, Linck, Netter, and Yang (2008) also find that performance does not appear to drive CEO duality. In contrast, Wintoki, Linck, and Netter (2012) provide evidence that CEO duality may be a function of past values of firm performance and hence not strictly exogenous.