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

We identified 11,023 unique URLs referring to the origin of COVID-19 appearing in 267,084 Facebook, Twitter, Reddit, and 4chan posts between January and March 2020. We classified them based on their source (mainstream, alternative, other) and their content (supporting conspiracy theories, used as evidence for conspiracy theories, neither). We considered URLs in the first two content categories as stories reinforcing conspiracy theories. We investigated whether posts containing these stories were removed or labeled as such by the platforms. Then, we employed appropriate statistical techniques to quantify conspiracy theory diffusion between...