Abstract
The purpose of this study is to analyze how altruistic behavior can be maintained in a group with flexible membership. In this paper, altruistic behaviors are limited to individual-focused net generalized exchange, in which members provide resources to benefit one member at a time. In preceding works, it was shown that this exchange can be maintained in a fixed and long-term relationship at the group and community levels, where reputations are widely known and punishments are easily conducted. However, it can also be maintained in a group with flexible membership. The mechanism of this puzzling phenomenon can be clarified by field survey and mathematical modeling.
The analysis focuses on joint labor disputes in community unions. Community unions are individual-affiliate unions in which members can easily join and drop out. They are for both regular workers who cannot get any support from their firmaffiliate unions and non-regular workers who cannot join a firm-affiliate union. Joint labor disputes are seen as the generalized exchange because in these disputes, interested people can get support from the rest of the members of their union. The game theoretic model shows that the conditional altruistic strategy can be a subgame perfect Nash equilibrium, even when none of the previous requirements are satisfied. The mechanism is that the players punish free riders, and the flexible relationship requires not only exiting, but also entering in a regular way. They make it possible to maintain the indirect reciprocal system. Moreover, the model shows that if players live too long, the level of cooperation may not be maintained.
