Liquid Democracy with Ranked Delegations

TL;DR

This paper explores a generalized liquid democracy model allowing agents to specify multiple ranked delegates, analyzing delegation rules through axiomatic and experimental methods to optimize participation and power distribution.

Contribution

It introduces a formal framework for multi-path delegation rules in liquid democracy, including axiomatic characterizations, impossibility results, and novel rules with desirable properties.

Findings

Delegation rules can be characterized axiomatically.

An impossibility result limits certain rule combinations.

Experimental analysis shows trade-offs in rule performance.

Abstract

Liquid democracy is a novel paradigm for collective decision-making that gives agents the choice between casting a direct vote or delegating their vote to another agent. We consider a generalization of the standard liquid democracy setting by allowing agents to specify multiple potential delegates, together with a preference ranking among them. This generalization increases the number of possible delegation paths and enables higher participation rates because fewer votes are lost due to delegation cycles or abstaining agents. In order to implement this generalization of liquid democracy, we need to find a principled way of choosing between multiple delegation paths. In this paper, we provide a thorough axiomatic analysis of the space of delegation rules, i.e., functions assigning a feasible delegation path to each delegating agent. In particular, we prove axiomatic characterizations as well as an impossibility result for delegation rules. We also analyze requirements on delegation rules that have been suggested by practitioners, and introduce novel rules with attractive properties. By performing an extensive experimental analysis on synthetic as well as real-world data, we compare delegation rules with respect to several quantitative criteria relating to the chosen paths and the resulting distribution of voting power. Our experiments reveal that delegation rules can be aligned on a spectrum reflecting an inherent trade-off between competing objectives.