We study two-stage committee elections where voters have dynamic preferences over candidates; at each stage, a committee is chosen under a given voting rule. We are interested in identifying a winning committee for the second stage that overlaps as much as possible with the first-stage committee. We show a full complexity dichotomy for the class of Thiele rules: this problem is tractable for Approval Voting (AV) and hard for all other Thiele rules (including, in particular, Proportional Approval Voting and the Chamberlin-Courant rule). We extend this dichotomy to the greedy variants of Thiele rules. We also explore this problem from a parameterized complexity perspective for several natural parameters. We complement the theory with experimental analysis: e.g., we investigate the average number of changes in the committee as a function of changes in voters' preferences and the role of ties.

本研究解决了一个动态偏好的选民如何在两阶段委员会选举中选择最终胜出委员会的问题，特别关注第二阶段的委员会如何尽可能与第一阶段重叠。我们对Thiele规则的复杂性进行全面分析，发现批准投票是可处理的，而其他Thiele规则则普遍为难题，进一步通过实验分析补充理论结果。

多赢家临时投票及对变化的厌恶