This paper selects 21838 test samples of China′s A-share listed companies from 1999 to 2015, in order to control heteroscedasticity and intragroup correlation problems, by using Cluster regression to examine how CEO duality, big shareholders′ control and the interactive effect impact investment efficiency. It shows that investment efficiency of duality firms significantly lower than non-duality firms. But CEO duality does not significantly affect investment efficiency in firms with lower degree of ownership concentration. CEO duality reduces more investment efficiency to firms with higher degree of ownership concentration. CEO duality is positively associated with inefficient investment in the firms with higher degree of ownership concentration. Moreover, the proportion of share held by the first big shareholders is positively associated with investment efficiency in the non-duality firms. The higher proportion of share held by the first big shareholders causes more inefficient investment to duality firms. The proportion of share held by the first big shareholders is positively associated with inefficient investment in the duality firms. 

This paper has the following two contributions: First of all, this article from the angle of investment efficiency, studies CEO duality influence on economic efficiency, it is directly from a specific influence on the way to test CEO duality influence on economic efficiency, and by investigating, under different ownership concentration, how CEO duality impacts investment efficiency. It shows that CEO duality is not always can reduce investment efficiency, only CEO duality of higher ownership concentration company can reduce investment efficiency, CEO duality of lower equity concentration company can not significantly affect investment efficiency. It provides with the existing literature of studying the relation between investment efficiency and CEO duality different empirical evidence, thus it deepens the research on the influence of CEO duality on investment efficiency. Second, by looking at two different position conditions, the big shareholder control impact on investment efficiency, this paper finds big shareholder control does not always lower investment efficiency, big shareholder control reduce investment efficiency only in CEO duality company, and big shareholder control can improve investment efficiency in the two separate company. It provides with the existing literature of studying the relation between investment efficiency and big shareholder control of different empirical evidence, thus deepens the study of relationship between large shareholder control and investment efficiency, and enriches the economic consequences of large shareholder control research.

The research conclusion of this paper has the following implications to enterprise managers, investors, and government regulators: firstly, for enterprise managers, managers in view of the specific decision problem, can choose by adjusting the enterprise decision-making configuration status, or dispersed ownership concentration to improve efficiency of decision making, also can choose and adjust corporate decision-making configuration and ownership concentration to improve efficiency of business decisions. Secondly, for investors, investors should choose those companies with decentralized decision-making rights to better supervise and control the managers. Finally, for the government regulators, regulators should pay more attention to strengthen the supervision of the control of major shareholders in companies with CEO duality, because the negative impact of control of major shareholders on the decision-making efficiency will be more obvious in companies with CEO duality.