Certification of Distributional Individual Fairness
This work addresses the need for scalable formal fairness guarantees in machine learning, offering a practical solution for certifying individual fairness in real-world applications, though it builds incrementally on prior certification techniques.
The paper tackles the problem of certifying individual fairness for neural networks by introducing a method to certify distributional individual fairness, which scales to networks orders of magnitude larger than prior methods and provides efficient bounds under distribution shifts.
Providing formal guarantees of algorithmic fairness is of paramount importance to socially responsible deployment of machine learning algorithms. In this work, we study formal guarantees, i.e., certificates, for individual fairness (IF) of neural networks. We start by introducing a novel convex approximation of IF constraints that exponentially decreases the computational cost of providing formal guarantees of local individual fairness. We highlight that prior methods are constrained by their focus on global IF certification and can therefore only scale to models with a few dozen hidden neurons, thus limiting their practical impact. We propose to certify distributional individual fairness which ensures that for a given empirical distribution and all distributions within a $γ$-Wasserstein ball, the neural network has guaranteed individually fair predictions. Leveraging developments in quasi-convex optimization, we provide novel and efficient certified bounds on distributional individual fairness and show that our method allows us to certify and regularize neural networks that are several orders of magnitude larger than those considered by prior works. Moreover, we study real-world distribution shifts and find our bounds to be a scalable, practical, and sound source of IF guarantees.