Recommender Systems Fairness Evaluation via Generalized Cross Entropy

Published in Workshop on Recommendation in Multistakeholder Environments (RMSE) as part of ACM RecSys 2019, 2019

Recommended citation: Yashar Deldjoo, Vito Walter Anelli, Hamed Zamani, Alejandro Bellogin, Tommaso Di Noia Workshop on Recommendation in Multistakeholder Environments.

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Abstract

Fairness in recommender systems has been considered with respect to sensitive attributes of users (eg, gender, race) or items (eg, revenue in a multistakeholder setting). Regardless, the concept has been commonly interpreted as some form of equality–ie, the degree to which the system is meeting the information needs of all its users in an equal sense. In this paper, we argue that fairness in recommender systems does not necessarily imply equality, but instead it should consider a distribution of resources based on merits and needs. We present a probabilistic framework based on generalized cross entropy to evaluate fairness of recommender systems under this perspective, where we show that the proposed framework is flexible and explanatory by allowing to incorporate domain knowledge (through an ideal fair distribution) that can help to understand which item or user aspects a recommendation algorithm is over-or under-representing. Results on two real-world datasets show the merits of the proposed evaluation framework both in terms of user and item fairness.