Fairness-Aware Meta-Learning via Nash Bargaining
This work addresses fairness issues for sensitive groups in ML models, offering a novel method to enhance fairness without compromising performance, though it is incremental in its approach.
The paper tackles group-level fairness in machine learning by proposing a two-stage meta-learning framework that resolves hypergradient conflicts using Nash Bargaining to improve stability and fairness, with empirical validation across multiple datasets and tasks.
To address issues of group-level fairness in machine learning, it is natural to adjust model parameters based on specific fairness objectives over a sensitive-attributed validation set. Such an adjustment procedure can be cast within a meta-learning framework. However, naive integration of fairness goals via meta-learning can cause hypergradient conflicts for subgroups, resulting in unstable convergence and compromising model performance and fairness. To navigate this issue, we frame the resolution of hypergradient conflicts as a multi-player cooperative bargaining game. We introduce a two-stage meta-learning framework in which the first stage involves the use of a Nash Bargaining Solution (NBS) to resolve hypergradient conflicts and steer the model toward the Pareto front, and the second stage optimizes with respect to specific fairness goals. Our method is supported by theoretical results, notably a proof of the NBS for gradient aggregation free from linear independence assumptions, a proof of Pareto improvement, and a proof of monotonic improvement in validation loss. We also show empirical effects across various fairness objectives in six key fairness datasets and two image classification tasks.