A Game Theoretical Analysis of Cooperation and Coalition Formation

本研究的目的是运用博弈论中的新方法，探讨追求自身价值的经济主体之间自愿合作和联盟形成的条件和机制。本研究包括以下三个主题：自愿合作与联盟形成。(1)合作与联盟形成的非合作议价模型我们提出了一个一般n人战略博弈的非合作顺序议价模型，其中一组参与者的合作可能会对其他参与者产生外部性。我们首先定义一个n人策略博弈的核心概念，叫做纳什核心。纳什核心是一种关于收益分配有效性的新概念，它基于这样一种观点，即当一个联盟形成时，恭维联盟的回应应该与他们谈判的纳什议价方案一致。证明了当且仅当博弈的纳什议价解属于纳什核心时，博弈模型的平稳子博弈完美均衡中存在最大的博弈群体。此外，谈判产生纳什议价解决方案的结果。我们设计并进行议价实验来检验理论预测。研究表明，联盟形成的议价结果在很大程度上受到主体相互行为的影响。(2)群体形成的进化分析提出了群体形成的进化博弈模型，并探讨了异质性偏好如何影响群体形成的长期均衡。(3)经济应用：将研究中建立的理论模型应用于《京都议定书》气候变化国际谈判。本文基于欧盟、前苏联、日本和美国的实际排放数据，研究了非合作议价模型如何解释《京都议定书》中商定的二氧化碳减排。

The aim of this research is to investigate conditions and mechanisms for voluntary cooperation and coalition formation among economic agents pursuing their own values, by applying new methodologies in game theory. The research consists of the following three topics about voluntary cooperation and coalition formation.(1) noncooperative bargaining models for cooperation and coalition formationWe present a noncooperative sequential bargaining model for a general n-person strategic game where cooperation by a group of players may induce externality to other players. We first define a new notion of the core, called the Nash core, of the n-person strategic game. The Nash-core is defined by a new notion of effectiveness of a payoff allocation, which is based on the idea that when a coalition forms, a response by, the compliment coalition should be consistent with the Nash bargaining solution of their negotiations. We prove that the largest group of players forms in a stationary subgame perfect equilibrium of the bargaining model if and only if the Nash bargaining solution of the game belongs to the Nash core. Moreover, negotiations result in the Nash bargaining solution outcome. We design and conduct bargaining experiments to test theoretical predictions. We show that bargaining outcomes of coalition formation are substantially influenced by reciprocal behavior of subjects.(2) evolutionary analysis of group formationWe present an evolutionary game model for group formation in the collective action problem and investigate how heterogeneous preferences affect a long-run equilibrium for group formation.(3) economic applicationsWe apply theoretical models developed in the research to international negotiations on climate change in the Kyoto protocol. We investigate how noncooperative bargaining models can explain the C02 emissions reduction agreed in the Kyoto protocol, based on actual data about emissions by EU, Former Soviet Union, Japan and USA.