小選挙区比例代表並立制に関するゲーム論的一考察

抄録

In the context of “Shou-senkyoku=Hirei-daihyou=Heiritsu-sei, “Duverger's Law” will be studied using a game theoretical model. The main result is two theorems. The Negative Theorem is that exit from an election, which means implicit alliance, occurs only if the Condorcet winner is not the biggest party. The Positive Theorem is that except for the case of a chicken game without suitable focal point, the Condorcet winner always wins the election in the equilibrium.