Fair Multi-agent Persuasion with Submodular Constraints

TL;DR

This paper introduces a signaling policy for Bayesian persuasion in multi-agent settings with submodular constraints, achieving near-optimal fairness in utility distribution among agents.

Contribution

It presents a novel approach to fairness in multi-agent persuasion, using majorization and polymatroid structures, with an efficient approximation algorithm.

Findings

Achieves logarithmic approximation to fair utility distribution

Structural characterization of agent utilities as base polytopes

Polynomial-time approximation via multiplicative weights update

Abstract

We study the problem of selection in the context of Bayesian persuasion. We are given multiple agents with hidden values (or quality scores), to whom resources must be allocated by a welfare-maximizing decision-maker. An intermediary with knowledge of the agents' values seeks to influence the outcome of the selection by designing informative signals and providing tie-breaking policies, so that when the receiver maximizes welfare over the resulting posteriors, the expected utilities of the agents (where utility is defined as allocation times value) achieve certain fairness properties. The fairness measure we will use is majorization, which simultaneously approximately maximizes all symmetric, monotone, concave functions of the utilities. We consider the general setting where the allocation to the agents needs to respect arbitrary submodular constraints, as given by the corresponding polymatroid. We present a signaling policy that, under a mild bounded rationality assumption on the receiver, achieves a logarithmically approximate majorized policy in this setting. The approximation ratio is almost best possible, and that significantly outperforms generic results that only yield linear approximations. A key component of our result is a structural characterization showing that the vector of agent utilities for a given signaling policy defines the base polytope of a different polymatroid, a result that may be of independent interest. In addition, we show that an arbitrarily good additive approximation to this vector can be produced in (weakly) polynomial time via the multiplicative weights update method.