Fast solution to the fair ranking problem using the Sinkhorn algorithm
This work addresses the practical scalability issue of fair ranking for recommender systems in online marketplaces, offering a significant speed improvement over prior methods.
The paper tackles the challenge of efficiently computing fair rankings in two-sided marketplaces by proposing a fast algorithm that transforms the problem into an unconstrained optimization and uses the Sinkhorn algorithm in a gradient ascent method. The result is a method that produces high-quality fair rankings and is approximately 1000 times faster than using commercial optimization software.
In two-sided marketplaces such as online flea markets, recommender systems for providing consumers with personalized item rankings play a key role in promoting transactions between providers and consumers. Meanwhile, two-sided marketplaces face the problem of balancing consumer satisfaction and fairness among items to stimulate activity of item providers. Saito and Joachims (2022) devised an impact-based fair ranking method for maximizing the Nash social welfare based on fair division; however, this method, which requires solving a large-scale constrained nonlinear optimization problem, is very difficult to apply to practical-scale recommender systems. We thus propose a fast solution to the impact-based fair ranking problem. We first transform the fair ranking problem into an unconstrained optimization problem and then design a gradient ascent method that repeatedly executes the Sinkhorn algorithm. Experimental results demonstrate that our algorithm provides fair rankings of high quality and is about 1000 times faster than application of commercial optimization software.