Anyone but him: The complexity of precluding an alternative

Preference aggregation in a multiagent setting is a central issue in both human and computer contexts. In this paper, we study in terms of complexity the vulnerability of preference aggregation to destructive control. That is, we study the ability of an election’s chair to, through such mechanisms as voter/candidate addition/suppression/partition, ensure that a particular candidate (equivalently, alternative) does not win. And we study the extent to which election systems can make it impossible, or computationally costly (NP-complete), for the chair to execute such control. Among the systems we study—plurality, Condorcet, and approval voting—we find cases where systems immune or computationally resistant to a chair choosing the winner nonetheless are vulnerable to the chair blocking a victory. Beyond that, we see that among our studied systems no one system offers the best protection against destructive control. Rather, the choice of a preference aggregation system will depend ...

• Type: Journal
• Year: 2007
• Where: AI
• Authors: Edith Hemaspaandra, Lane A. Hemaspaandra, Jörg Rothe
• Keywords: AI 2007, Artificial Intelligence, Multiagent Setting, Preference Aggregation, Systems