PPP项目运营期间需求量下降情形下的补偿机制研究

PPP Projects: A Study of Compensation Mechanism with Unmet Demand

本文以最终用户付费的交通类PPP项目为分析对象,研究需求风险发生后政府如何采用需求量补偿机制以实现私人部门收益和消费者剩余的帕累托改进。本文构建了私人部门收益和消费者剩余模型,分析、比较了价格上限不变和价格上限可重新设定两种情形下需求量补偿机制对私人部门收益和消费者剩余的影响,分析了该补偿机制能够实现帕累托改进的条件,同时通过算例进行了仿真验证。结果表明:(1)在价格上限不变的情形下,需求量补偿机制只会诱导私人部门提高收费价格,损害消费者剩余,此时并不存在有效的需求量补偿范围;(2)当政府重新设定合理的价格上限并且双方的重新谈判成本较低时,存在有效的需求量补偿范围来实现私人部门收益和消费者剩余的帕累托改进。

Public-Private Partnership （PPP）, as an innovative way to provide infrastructure by the private sector, is widely adopted throughout the world. One of the most important risks faced by the private sector is demand risk. For years researchers have focused on how this kind of risk should be distributed between the government and the private sector. Some researchers argue that parties subject to losses should undertake the risk, which will help stimulate them to do better risk control. However, the demand risk is exogenous and thus cannot be prevented or controlled by either party. Considering the cooperation feature of PPP between the government and the private sector, the demand risk should be shared by both parties. Researchers put forward that signing ex ante guarantee arrangement with the government can be regarded as a method to reduce the risk losses of the private sector. However, the demand guaranteed by the government is specified at the time of contract signing before the occurrence of risk, problems of overcompensation or undercompensation may emerge due to bounded rationality. Therefore, currently researches have shifted their attention to how the compensation amount should be determined by the government when the demand risk occurs. At present, there are two research gaps with regard to this issue. First, scholars failed to take into consideration the calculation method of compensation amount in their studies, leading to ambiguity and even possible occurrence of corruption as perceived by the public when the government honours compensation. To solve this problem, the demand compensation mechanism should be proposed and detailed, thus making the compensation process a transparent one. Second, previous studies only focused on efficiency improvement, leaving fairness of distribution neglected, which is harmful to the sustainable development of PPP projects. Therefore, both of private sector＇s benefits and consumer surplus should be paid attention to when the government compensates the private sector so that a win-win situation can be achieved. To fill these gaps, our study focuses on conditions of Pareto-improvement for both private sector＇s benefits and consumer surplus under demand compensation mechanism in PPP transportation infrastructures whose revenue depends on charges collected from users. We first analyze how the demand compensation mechanism affects the private sector＇s profit and consumer surplus when the ceiling price is fixed. Results indicate that in this situation the mechanism improves private sector＇s benefits by an increasing price while damaging consumer surplus. Therefore, to realize both parties＇ Pareto-improvement, the government should first reset the ceiling price. This study then explores the impact of demand compensation mechanism when the ceiling price is reset. Results show that effective zone of compensation amount exists to realize Pareto-improvement when both parties＇ renegotiation costs are low. In addition, numerical examples are applied to test and verify these results. In summary, the demand compensation mechanism can realize Pareto-improvement when the ceiling price is allowed to be reset and the renegotiation costs for both parties are low. Our study results are of significance for the government to make correct decisions on compensation amount, and provide theoretical guidance for risk sharing between public and private sectors such that sustainable development of PPP projects can be promoted. Key words： public-private partnership; renegotiation; demand risk; compensation mechanism