【时间】2026年9月11日（星期五）下午14:00

【地点】大学城校园经济与管理学院文二栋301会议室

【主题】Plurality voting games: Winning coalitions and voting power

【主讲人】Agnieszka RUSINOWSKA

【主持人】韩卫彬副教授

【主讲人简介】Agnieszka RUSINOWSKA is a CNRS Research Professor (Directrice de Recherche DRCE1) in economics, working at Centre d’Economie de la Sorbonne (CES, CNRS & University Paris 1). Agnieszka RUSINOWSKA is a microeconomic-theorist working on network theory (opinion dynamics, influence, network formation), game theory and coalition formation (cooperative games, bargaining), social choice and voting, and has some research experience in experimental economics. She publishes regularly in peer-reviewed leading journals (over 60 articles) in economics and operations research, including e.g., Journal of Economic Theory, Operations Research, Mathematics of Operations Research, Games and Economic Behavior, Journal of Economic Dynamic and Control, Economic Theory, etc.

【摘要】Simple games in partition function form are used to model voting situations where a coalition being winning or losing might depend on the way players outside that coalition organize themselves. In this lecture, we consider plurality voting games being simple games in partition function form such that in every partition there is at least one winning coalition. Such a game is said to be weighted if it is possible to assign weights to the players such that a winning coalition in a partition is always one which maximizes the sum of the weights of its members over all coalitions in the partition. A plurality game is decisive if in every partition there is exactly one winning coalition. In van den Brink et al. (2021) we show that plurality games need not be weighted, even not when they are decisive. We prove that (i) decisive plurality games with at most four players, (ii) majority games with an arbitrary number of players, and (iii) decisive plurality games that exhibit some kind of symmetry, are weighted. Complete characterizations of the winning coalitions in the corresponding partitions are provided. In our follow up article, van den Brink et al. (2025), we introduce an equal impact power index for this class of games and provide an axiomatic characterization. This power index is based on equal weight for every partition, equal weight for every winning coalition in a partition, and equal weight for each player in a winning coalition. Since some of our axioms are conditioned on the power impact of losing coalitions becoming winning in a partition, our characterization depends on a new result showing the existence of such elementary transitions between plurality games in terms of single embedded winning coalitions. The axioms restrict the impact of such transitions on the power of different types of players.