Achieving Fairness Across Local and Global Models in Federated Learning

Achieving fairness across diverse clients in Federated Learning (FL) remains a significant challenge due to the heterogeneity of the data and the inaccessibility of sensitive attributes from clients' private datasets. This study addresses this issue by introducing EquiFL, a novel approach designed to enhance both local and global fairness in federated learning environments. EquiFL incorporates a fairness term into the local optimization objective, effectively balancing local performance and fairness. The proposed coordination mechanism also prevents bias from propagating across clients during the collaboration phase. Through extensive experiments across multiple benchmarks, we demonstrate that EquiFL not only strikes a better balance between accuracy and fairness locally at each client but also achieves global fairness. The results also indicate that EquiFL ensures uniform performance distribution among clients, thus contributing to performance fairness. Furthermore, we showcase the benefits of EquiFL in a real-world distributed dataset from a healthcare application, specifically in predicting the effects of treatments on patients across various hospital locations.