Proceedings

Measuring a Priori Voting Power in Liquid Democracy

Rachael Colley, Théo Delemazure, Hugo Gilbert

Proceedings of the Thirty-Second International Joint Conference on Artificial Intelligence

Main Track. Pages 2607-2615.

https://doi.org/10.24963/ijcai.2023/290

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Abstract

We introduce new power indices to measure the a priori voting power of voters in liquid democracy elections where an underlying network restricts delegations. We argue that our power indices are natural extensions of the standard Penrose-Banzhaf index in simple voting games.

We show that computing the criticality of a voter is #P-hard even in weighted games with weights polynomially-bounded in the size of the instance.

However, for specific settings, such as when the underlying network is a bipartite or complete graph, recursive formulas can compute these indices for weighted voting games in pseudo-polynomial time.

We highlight their theoretical properties and provide numerical results to illustrate how restricting the possible delegations can alter voters' voting power.

Keywords

  • Game Theory and Economic Paradigms: GTEP: Computational social choice
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