Bribery Can Get Harder in Structured Multiwinner Approval Election

TL;DR

This paper investigates the computational complexity of bribery in structured multiwinner approval elections, revealing that such structures can sometimes make manipulation harder, contrary to common assumptions.

Contribution

It introduces complexity results for bribery problems in structured elections, considering both constructive and destructive cases, with a focus on candidate and voter interval properties.

Findings

Structured elections can increase bribery complexity.

Bribery remains feasible within certain budget constraints.

Preliminary insights into destructive bribery variants are provided.

Abstract

We study the complexity of constructive bribery in the context of structured multiwinner approval elections. Given such an election, we ask whether a certain candidate can join the winning committee by adding, deleting, or swapping approvals, where each such action comes at a cost and we are limited by a budget. We assume our elections to either have the candidate interval or the voter interval property, and we require the property to hold also after the bribery. While structured elections usually make manipulative attacks significantly easier, our work also shows examples of the opposite behavior. We conclude by presenting preliminary insights regarding the destructive variant of our problem.