Coordination in Large Numbers: An Agent-Based Model of International Negotiations


  • Author’s note: I am indebted to Kurt Taylor Gaubatz, Neil Harrison, Steve Yetiv, and three anonymous reviewers for constructive criticism on previous drafts of this article, and to Timothy Breslin and Jack Covarrubias for their research assistance. I also thank the participants of the International Workshop on Complexity and Policy Analysis, University College-Cork, June 22–24, 2005, who provided constructive commentary on some of the algorithms presented in this article. Any and all errors are my sole responsibility. Replication data and command files are available via the Dataverse Network Project ( and the ISA data archive page (


How do states solve n-choice cooperation problems? Although classical game theory offers useful insights into how states achieve cooperation, its focus on equilibria means that it is largely silent on the processes of negotiation, particularly when multiple solutions to a cooperation problem exist. To explore the path histories of international cooperation, this article uses an agent-based model to explore how states solve a coordination game with three equilibria. To further enrich the analysis, the model explores how domestic constraints may affect coordination games. Such state-level constraints may present negotiators with considerable informational costs and high barriers to understanding each other’s preferences. The model finds that the process of communicating preferences can greatly affect the prospects for cooperation, independent of distributional consequences and concerns about cheating. It also finds that, contrary to collective goods theory, a large number of states coordinate a solution to the problem easier than small groups. This is because larger groups create denser networks that communicate preferences more efficiently. The agent-based model thus illustrates how simulation as a method can challenge our extant thinking about cooperation among nation-states. These findings have implications for research on interstate coordination, since it suggests transnational linkages may help states overcome information barriers that frustrate agreements.