Social media sentiment contagion and stock price jumps and crashes

Inspired by the SIR model, we adopt sentiment extracted from the social media platform (Guba) of Eastmoney in China during 2008–2022 to construct a firm-specific investor sentiment contagion speed measurement and investigate the association between sentiment contagion speed and stock price jumps and crashes. Specifically, we find that the contagion of optimistic sentiment is positively associated with jumps in stock price, while the contagion of pessimistic sentiment is positively associated with the crash risk of stock prices. Moreover, these associations vary based on the prevailing proportion of the sentiment and the market's bull and bear status. Additionally, the stock price movement associated with social sentiment contagion is influenced by short-selling constraints, analyst coverage and institutional ownership.