Indirect information exchange

The goal of this paper is to show that when agents can engage in second-hand trading of information, some agents may not be able to exchange their information with other agents. With three agents, such foreclosure is possible only when agents can refuse to exchange information. With four or more players, foreclosure is possible even when players cannot abstain from or refuse to trade, but it does not constitute a subgame perfect equilibrium. Players can avoid being foreclosed by choosing what to trade and with whom. The results can be applied to formal and informal information sharing, file sharing systems and peer-to-peer networks. Copyright Kluwer Academic Publishers 2004