Abstract
This thesis deals with the collectiver action problem, also called the free-rider problem, first raised by Olson (1965). He stipulates that if self-interested and rational agents participate in a collective action, due to the impossibility of excluding the agents from the benefits of that action, the latter have every interest in not contributing to the action, while benefiting from the contribution of other collective action contributors. Based on this problem, this thesis focuses on the levels of individual effort and the effectiveness of a group to provide a collective effort in different frameworks of collective actions.In our first chapter, we look at the effect of group size on individual efforts and the effectiveness of a group in achieving its goals. We assume two groups distinguished only by their size, which compete for a good that may be more or less divisible among the members of the wining group. Our main contribution is to analyse how the complementarity group members’ efforts impacts the relationship between the size of the group and its effectiveness. We show that the complementarity between group members' efforts can reverse the paradox of group size. A paradox that means that a smaller group is more effective than a larger group in achieving its goal. We also show that the complementarity between group members’ efforts allows the agents of the larger group to get a greater net gain than the agents of the smaller group, even if the contested good is perfectly divisible between the members of the wining group.The second chapter focuses on the distribution of the burden of the collective action in a heterogeneous group, where each agent values collective action to a different degree. We seek to explain theoretically how the distribution of the burden of collective action varies in function of various parameters. We assume agents that value to varying degrees a public good they provide, assuming a degree of complementarity between agents' efforts. We show that the complementarity between the agents' efforts benefits the agent who has the highest valuation of the collective action in terms of the distribution of the burden of the collective action. Then, we assume that the agents are no longer perfectly self-intesrested and we show that the benevolence between the agents benefits the agent with the highest valuation of the collective action in terms of distribution of the burden of the collective effort.The third chapter analyses the trade-off that can be made by agents between making a conflict effort and contributing to a public good. We analyze this trade-off in assuming that the economic environment is degraded. Thus, we seek to determine the economic incentives that impact the trade-off that can be made by agents between a conflict effort or a collective effort, when the economic environment is deteriorating. We assume an individual utility function that depends on the one hand, a resource that can be taken up individually through a conflict, and on the other hand, a public good provided by voluntary individual contributions of agents. We also assume that gains from conflict and the provision of the public good are separately degraded by an exogenous parameter. We show that agents are encouraged to make a conflict effort when the gains of the conflict are directly diminished, but they are encouraged to increase their supply of the public good when it is directly diminished. We also analyze the relationship between the effort and the amount of conflict resource. We show that the sign of the relationship between the conflict effort and the amount of conflict resource is not monotonous and depends in particular on the level of degradation that negatively impacts the gains of the conflict.