基于私人过度自信的PPP项目最优补偿契约设计与选择

基于政府对PPP项目补偿决策的困境,引入一种单期补偿契约,同时考虑到私人投资者在政府补偿下会存在过度自信倾向,通过“均值-方差”描述而引入私人过度自信系数,建立私人投资的期望效用函数,从而运用主从博弈方法分析私人过度投资行为以及对政府最优补偿契约的影响,进而在私人过度自信不可观察情形下,讨论政府最优补偿契约的设计与选择。研究表明：虽然私人过度投资行为并不一定有助于项目预期社会效益改善,但政府总可通过相应地调整契约参数来设计适应私人不同过度自信行为的最优补偿契约,并当私人过度投资不可观测时,可根据其过度自信的概率分布情况来选择使项目预期社会效益比较大的最优补偿契约。研究结果不仅有利于政府的补偿决策,也为PPP项目的实施提供了一种较好的理论支持。

Design and Selection of Optimal Compensation Contract for PPP Project Based on Private Overconfidence

The current new-type urbanization measures of Chinese government will pull tens of thousands of billions of investment in the infrastructure. However, the government's financial capital is so limited that it is difficult to meet the demand of a large number of infrastructure investment. Thus a model called PPP (Private-Public Partnership) is put forward to solve the shortage of government funding. The infrastructure project using the PPP generally has a quasi public goods attribute, which leads to its low operating revenue unable to take back the private huge initial investment. That means the proper compensation should be given to the private investor, if the government wants the PPP project to be successful. The compensation for the PPP project is not easy to determine before the event because the excessive or insufficient compensation will cause that the project's social welfare or the private interest is damaged. Only the compensation after the event will reduce the enthusiasm of private investment, which will also cause the compensation to be inefficient. Based on the governmental decision-making dilemma for the compensation, a single period compensation contract is introduced for the private investor. The contract specifies that the government should promise the concession revenue before the event to the private investor and then give a certain post-compensation to the investor by comparing the project's real revenue with the concession revenue.When the contract is accepted, the governmental compensation is likely to imply that the private investor show the excessive optimism and confidence on the PPP project's future expectation. That is,the private investor has the overconfidence behavior under the governmental compensation. For this reason, the private overconfidence is considered in the study on the governmental compensation contract for the PPP project.Firstly,the private investor's overconfidence is described by the "Mean-Variance" in which the private overconfidence coefficient is introduced. Thus the private expected utility function related to the overconfidence preference is proposed. Accordingly, the private overconfidence investment strategy is given out and its effect on the governmental optimal compensation contract is studied by the method of Stackelberg game. Secondly, under the circumstance that the private overconfidence can't be observed, the design and selection of governmental optimal compensation contract is discussed. Finally, the obtained conclusions are verified and expanded through a computing example.The studying results show that the private excessive investment behavior doesn't necessarily help to improve the expected social benefits for the project, but the government can always adjust the contract parameter to design the optimal compensation contract (maximizing the project's expected social benefit) which can adapt to the private different overconfidence behavior, and when the private excessive investment can't be observed, the government can select the optimal contract leading to the project's larger expected benefit according to the probability distribution for the private overconfidence.In summary, the results obtained in this paper not only contribute to the governmental compensation strategy, but also provide a better theoretical support for the implement of PPP project.