The spread of COVID-19 conspiracy theories on social media and the effect of content moderation

We investigate the diffusion of conspiracy theories related to the origin of COVID-19 on social media. By analyzing third-party content on four social media platforms, we show that: (a) In contrast to conventional wisdom, mainstream sources contribute overall more to conspiracy theories diffusion than alternative and other sources; and (b) Platforms’ content moderation practices are able to mitigate the spread of conspiracy theories. Nevertheless, we locate issues regarding the timeliness and magnitude of content modera-tion, as well as that platforms filter significantly fewer conspiracy theories coming from mainstream sources. Given this, we discuss policy steps that can contribute to the containment of conspiracy theories by media sources, platform owners, and users.