A Contribution to the Critique of Liquid Democracy

Caragiannis, Ioannis; Micha, Evi

doi:10.24963/ijcai.2019/17

Cited by 25 publications

(38 citation statements)

References 10 publications

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“…Finally, Caragiannis and Micha (2019) extend the model proposed by the conference version of this work and prove further impossibility results. In particular, they show that liquid democracy can be much worse than either direct democracy or a complete dictatorship, and they also demonstrate that the problem of optimally coordinating delegations in a centralized manner in order to maximize the probability of discovering the ground truth is NP-hard.…”

Section: Subsequent Related Worksupporting

confidence: 66%

Liquid Democracy: An Algorithmic Perspective

Kahng

Mackenzie

Procaccia

2021

jair

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We study liquid democracy, a collective decision making paradigm that allows voters to transitively delegate their votes, through an algorithmic lens. In our model, there are two alternatives, one correct and one incorrect, and we are interested in the probability that the majority opinion is correct. Our main question is whether there exist delegation mechanisms that are guaranteed to outperform direct voting, in the sense of being always at least as likely, and sometimes more likely, to make a correct decision. Even though we assume that voters can only delegate their votes to better-informed voters, we show that local delegation mechanisms, which only take the local neighborhood of each voter as input (and, arguably, capture the spirit of liquid democracy), cannot provide the foregoing guarantee. By contrast, we design a non-local delegation mechanism that does provably outperform direct voting under mild assumptions about voters.

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Section: Subsequent Related Worksupporting

confidence: 66%

Liquid Democracy: An Algorithmic Perspective

Kahng

Mackenzie

Procaccia

2021

jair

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“…Kahng, Mackenzie and Procaccia [30] as well as Caragiannis and Micha [10] have investigated the accuracy of the LD framework following this line of research. These two works that have been detailed in the introduction, are part of a recent trend in the AI literature trying to explore the algorithmic properties of new voting paradigms similar to LD [1,5,7,8,9,10,12,15,19,22,24,30,31,33,40,41]. We now shortly detail di erent questions addressed by these works.…”

Section: Related Workmentioning

confidence: 99%

When Can Liquid Democracy Unveil the Truth?

Becker¹,

D’Angelo²,

Delfaraz³

et al. 2021

Preprint

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Liquid democracy is a voting paradigm that allows voters that are part of a social network to either vote directly or delegate their voting rights to one of their neighbors. The delegations are transitive in the sense, that a voter who decides to delegate, delegates both her own vote and the ones she has received through delegations. The additional exibility of the paradigm allows to transfer voting power towards a subset of voters ideally containing the most expert voters on the question at hand. It is thus tempting to assume that liquid democracy can lead to more accurate decisions. This claim has been investigated recently, maybe most importantly, by Kahng, Mackenzie, and Procaccia [30] and Caragiannis and Micha [10], who provide however mostly negative results using a model similar to the uncertain dichotomous choice model.In this paper, we provide new insights on this question. In particular, we investigate the so-called ODP-problem that has been formulated by Caragiannis and Micha [10]. Here, we are in a setting with two election alternatives out of which one is assumed to be correct. In ODP, the goal is to organise the delegations in the social network in order to maximize the probability that the correct alternative, referred to as ground truth, is elected. While the problem is known to be computationally hard, we strengthen existing hardness results by providing a novel strong approximation hardness result: For any positive constant 𝐶, we prove that, unless 𝑃 = 𝑁 𝑃, there is no polynomial-time algorithm for ODP that achieves an approximation guarantee of 𝛼 ≥ (ln 𝑛) −𝐶 , where 𝑛 is the number of voters. The reduction designed for this result uses poorly connected social networks in which some voters su er from misinformation. Interestingly, under some hypothesis on either the accuracies of voters or the connectivity of the network, we obtain a polynomial-time 1/2-approximation algorithm. This observation proves formally that the connectivity of the social network is a key feature for the e ciency of the liquid democracy paradigm. Lastly, we run extensive simulations and observe that simple algorithms (working either in a centralized or decentralized way) outperform direct democracy on a large class of instances. Overall, our contributions yield new insights on the question in which situations liquid democracy can be bene cial.

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“…Other models of delegative democracy. Inspired by Kahng, Mackenzie, and Procaccia [34], Caragiannis and Micha [14] study the interplay of liquid democracy and truth-tracking. Assuming that voting is about finding some ground-truth, a delegation to another agent implies that you believe they will be better than you at finding the truth.…”

Section: Related Workmentioning

confidence: 99%

Unravelling multi-agent ranked delegations

Colley¹,

Grandi²,

Novaro³

2021

Preprint

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We introduce a voting model with multi-agent ranked delegations. This model generalises liquid democracy in two aspects: first, an agent's delegation can use the votes of multiple other agents to determine their own-for instance, an agent's vote may correspond to the majority outcome of the votes of a trusted group of agents; second, agents can submit a ranking over multiple delegations, so that a backup delegation can be used when their preferred delegations are involved in cycles. The main focus of this paper is the study of unravelling procedures that transform the delegation ballots received from the agents into a profile of direct votes, from which a winning alternative can then be determined by using a standard voting rule. We propose and study six such unravelling procedures, two based on optimisation and four using a greedy approach. We study both algorithmic and axiomatic properties, as well as related computational complexity problems of our unravelling procedures for different restrictions on the types of ballots that the agents can submit.

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A Contribution to the Critique of Liquid Democracy

Cited by 25 publications

References 10 publications

Liquid Democracy: An Algorithmic Perspective

Liquid Democracy: An Algorithmic Perspective

When Can Liquid Democracy Unveil the Truth?

Unravelling multi-agent ranked delegations

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