Empirical observation of negligible fairness–accuracy trade-offs in machine learning for public policy

Abstract

The growing use of machine learning in policy and social impact settings has raised concerns over fairness implications, especially for racial minorities. These concerns have generated considerable interest among machine learning and artificial intelligence researchers, who have developed new methods and established theoretical bounds for improving fairness, focusing on the source data, regularization and model training, or post-hoc adjustments to model scores. However, few studies have examined the practical trade-offs between fairness and accuracy in real-world settings to understand how these bounds and methods translate into policy choices and impact on society. Our empirical study fills this gap by investigating the impact of mitigating disparities on accuracy, focusing on the common context of using machine learning to inform benefit allocation in resource-constrained programmes across education, mental health, criminal justice and housing safety. Here we describe applied work in which we find fairness–accuracy trade-offs to be negligible in practice. In each setting studied, explicitly focusing on achieving equity and using our proposed post-hoc disparity mitigation methods, fairness was substantially improved without sacrificing accuracy. This observation was robust across policy contexts studied, scale of resources available for intervention, time and the relative size of the protected groups. These empirical results challenge a commonly held assumption that reducing disparities requires either accepting an appreciable drop in accuracy or the development of novel, complex methods, making reducing disparities in these applications more practical. A growing number of researchers are developing approaches to improve fairness in machine learning applications in areas such as healthcare, employment and social services, to avoid propagating and amplifying racial and other inequities. An empirical study explores the trade-off between increasing fairness and model accuracy across several social policy areas and finds that this trade-off is negligible in practice.