Effect of Social Media Posts on Stock Market During COVID-19 Infodemic: An Agenda Diffusion Approach

This study assesses the impact of social media posts by different categories of opinion leaders on the stock market during the coronavirus 2019 (COVID-19) infodemic. After aggregating tweets ( n = 302,806) into diverse agendas based on posters’ professional attributes, time-series analyses reveal that increased COVID-19 attention from media and public health agendas is linked to reduced stock prices. By contrast, emphasis on COVID-19 by political agendas tends to increase stock prices, contingent on public agenda sentiment levels due to negative bias. Additionally, the sentiment of the public agenda boosts stock prices through a chain mediating process. This study indicates that posts by politicians are more effective in preventing market crashes compared to those from media or public health experts. This research contributes to agenda-setting theory by introducing the agenda-diffusion approach, highlighting the distinct roles of opinion leaders, their dynamic effects, and the diffusion process. The findings provide insights for crisis management in future pandemics.