Collaboratively Adding Context to Social Media Posts Reduces the Sharing of False News

We build a novel database of around 285,000 notes from the Twitter CommunityNotes program to analyze the causal influence of appending contextualinformation to potentially misleading posts on their dissemination. Employing adifference in difference design, our findings reveal that adding context belowa tweet reduces the number of retweets by almost half. A significant, albeitsmaller, effect is observed when focusing on the number of replies or quotes.Community Notes also increase by 80its creator. The post-treatment impact is substantial, but the overall effecton tweet virality is contingent upon the timing of the contextual information'spublication. Our research concludes that, although crowdsourced fact-checkingis effective, its current speed may not be adequate to substantially reduce thedissemination of misleading information on social media.