The Terms of Cooperation’s Stability. What is the Reason of Flow Between Coalitions?

The following article presents an application of game-theoretical models, meant to describe and explain the conditions of stability of coalitions created within decision-making bodies. The basis of the presented approach is the concept of power indices, as well as subadditivity and superadditivity of coalitions. The article also illustrates how to apply the model of oceanic games for analyzing assemblies consisting of many participants. These studies are exemplified by the results of research on the decision-making processes in the Sejm (the lower house of the Polish parliament) and among delegates of the 2008 U.S. presidential nominations of the Democratic Party, which lead to clear, intuitive interpretations, useful for explanations of processes occurring within the decision-making bodies.