"Kelly is a Warm Person, Joseph is a Role Model": Gender Biases in LLM-Generated Reference Letters.

As generative language models advance, users have started to utilize Large Language Models (LLMs) to assist in writing various types of content, including professional documents such as recommendation letters. Despite their convenience, these applications introduce unprecedented fairness concerns. As generated reference letters might be directly utilized by users in professional or academic scenarios, they have the potential to cause direct social harms, such as lowering success rates for female applicants. Therefore, it is imminent and necessary to comprehensively study fairness issues and associated harms in such real-world use cases for future mitigation and monitoring. In this paper, we critically examine gender bias in LLM-generated reference letters. Inspired by findings in social science, we design evaluation methods to manifest gender biases in LLM-generated letters through 2 dimensions: biases in language style and biases in lexical content. Furthermore, we investigate the extent of bias propagation by separately analyze bias amplification in model-hallucinated contents, which we define to be the hallucination bias of model-generated documents. Through benchmarking evaluation on 4 popular LLMs, including ChatGPT, Alpaca, Vicuna and StableLM, our study reveals significant gender biases in LLM-generated recommendation letters. Our findings further point towards the importance and imminence to recognize biases in LLM-generated professional documents.