Symmetrized guaranteed utility mechanism minimizes risk in social choice
Risk-minimizing GUE-implementations of truthful reporting in a Dynamic Social Choice Problem
Computer Science and Game Theory
Summary
When groups need to make decisions over time, ensuring everyone reports their preferences truthfully is tricky, especially when balancing fairness and risk. The authors study a way to keep decisions efficient while minimizing uncertainty in what participants gain or lose. They find specific versions of an existing method (Guaranteed Utility Mechanism) that reduce the unpredictability of outcomes for everyone. This helps design systems where people have less reason to lie and face less financial risk.
What this means in practice
- •For economic mechanism designers: Design budget-balanced incentive schemes that minimize risk in repeated collective decisions where truthful reporting is needed.
- •For financial risk managers: Develop transfer rules that reduce variance in payouts among participants in dynamic risk-sharing agreements.
Authors
Endre Csóka, Máté Viczián
Abstract
The Guaranteed Utility Mechanism (GUM) was introduced to implement efficiency in Guaranteed Utility Equilibrium (GUE) in dynamic social choice problems. We show that this mechanism also has a previously unknown connection to risk minimization. Fixing an efficient decision policy, we study variance-minimizing budget-balanced transfer rules in the class of GUE-implementations of truthful reporting. A symmetrized version of GUM (sym-GUM) minimizes the sum of the agents' utility variances under truthful reporting when there is no public state. When a public state is present, a slight modification of this rule yields the minimizer for the same objective. Sym-GUM, however, does not minimize transfer risk. The minimizer for that problem is instead the symmetrized version of a closely related GUM-like transfer rule. In both problems, the minimizing truthful total transfers are unique up to agent-specific constants summing to zero and events of probability zero.