三方代建模式下共同代理问题研究

三方代建模式中政府投资单位、使用单位和代建单位三者之间是一种基于两个委托人和一个代理人的共同代理关系。运用共同代理理论构建三方代建模型，分析委托人（投资单位和使用单位）之间的利益冲突引发代理人（代建单位）道德风险的内在机制。假设投资单位和使用单位之间不存在利益冲突，通过单一委托代理模型分析投资节余分成制度对代建单位选择社会最优努力水准的激励机制。通过共同代理模型分析和解释了委托人之间的利益冲突导致投资节余分成制度激励失效，进而引发代建单位道德风险的原因。并对三方代建模式的适用条件进行分析，为工程实践中的契约设计提供参考。

Common Agency Problem in Tripartite Agent Construction Projects

The relationship among project investor，user and construction agent of an agent construction project is a common agency relationship which consists of two principals and one agent. In this paper，a tripartite agent construction scheme is formulated as a common agency model to investigate the mechanism of how a conflict between the two principals（investor and user）triggers construction agent’s moral hazard. Firstly，supposing there is no conflict between the principals in the single principal-agent model， the investment surplus sharing system is shown to be effective to encourage the construction agent to choose the social-optimal effort level. Then in the common agency model，we find that the conflict of interest between the two principals leads to an incentive failure of investment surplus sharing system，which further causes the moral hazard of construction agent. This paper lastly sheds light on application conditions which contribute to the contract design in the engineering practice.