Nonuniform Bribery

TL;DR

This paper introduces a nonuniform bribery model where voter prices depend on the specific change requested, providing polynomial algorithms for several voting protocols and NP-completeness results for weighted voters.

Contribution

It extends existing bribery models by allowing variable voter prices and offers algorithms and complexity results for various voting systems.

Findings

Polynomial-time algorithms for nonuniform bribery in multiple voting protocols.

NP-completeness results for weighted voter bribery problems.

Approximation algorithms, including an FPTAS, for NP-complete bribery problems.

Abstract

We study the concept of bribery in the situation where voters are willing to change their votes as we ask them, but where their prices depend on the nature of the change we request. Our model is an extension of the one of Faliszewski et al. [FHH06], where each voter has a single price for any change we may ask for. We show polynomial-time algorithms for our version of bribery for a broad range of voting protocols, including plurality, veto, approval, and utility based voting. In addition to our polynomial-time algorithms we provide NP-completeness results for a couple of our nonuniform bribery problems for weighted voters, and a couple of approximation algorithms for NP-complete bribery problems defined in [FHH06] (in particular, an FPTAS for plurality-weighted-$bribery problem).