A Study of Implicit Ranking Unfairness in Large Language Models

Chen Xu, Wenjie Wang, Yuxin Li, Liang Pang, Jun Xu, Tat-Seng Chua


Abstract
Recently, Large Language Models (LLMs) have demonstrated a superior ability to serve as ranking models. However, concerns have arisen as LLMs will exhibit discriminatory ranking behaviors based on users’ sensitive attributes (gender). Worse still, in this paper, we identify a subtler form of discrimination in LLMs, termed implicit ranking unfairness, where LLMs exhibit discriminatory ranking patterns based solely on non-sensitive user profiles, such as user names. Such implicit unfairness is more widespread but less noticeable, threatening the ethical foundation. To comprehensively explore such unfairness, our analysis will focus on three research aspects: (1) We propose an evaluation method to investigate the severity of implicit ranking unfairness. (2) We uncover the reasons for causing such unfairness. (3) To mitigate such unfairness effectively, we utilize a pair-wise regression method to conduct fair-aware data augmentation for LLM fine-tuning. The experiment demonstrates that our method outperforms existing approaches in ranking fairness, achieving this with only a small reduction in accuracy. Lastly, we emphasize the need for the community to identify and mitigate the implicit unfairness, aiming to avert the potential deterioration in the reinforced human-LLMs ecosystem deterioration.
Anthology ID:
2024.findings-emnlp.467
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2024
Month:
November
Year:
2024
Address:
Miami, Florida, USA
Editors:
Yaser Al-Onaizan, Mohit Bansal, Yun-Nung Chen
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
7957–7970
Language:
URL:
https://aclanthology.org/2024.findings-emnlp.467
DOI:
10.18653/v1/2024.findings-emnlp.467
Bibkey:
Cite (ACL):
Chen Xu, Wenjie Wang, Yuxin Li, Liang Pang, Jun Xu, and Tat-Seng Chua. 2024. A Study of Implicit Ranking Unfairness in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2024, pages 7957–7970, Miami, Florida, USA. Association for Computational Linguistics.
Cite (Informal):
A Study of Implicit Ranking Unfairness in Large Language Models (Xu et al., Findings 2024)
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PDF:
https://aclanthology.org/2024.findings-emnlp.467.pdf