社交媒体是否揭示了国有媒体的乐观偏见？来自中国的证据

摘要

State-controlled media, which is subject to political influence, tends to exhibit optimistic bias. In contrast, social media, which relies on the collective wisdom of crowds and generates information anonymously, is less likely to reflect politically induced optimistic bias. This paper investigates whether social media can serve as a benchmark for identifying the optimistic bias of statecontrolled media. Using articles from state-controlled newspapers and posts from online stock forums in China that discuss the same firms on the same days from 2009 to 2016, we find that social media can effectively identify the politically induced positive tone bias in state-controlled media. Furthermore, our stock return analysis shows that the market perceives state-controlled media as less informative when it is identified as optimistically biased, providing additional evidence that social media can serve as a reliable benchmark for detecting reporting bias.