A 120 Million Person Follow-Up to a 61 Million Person Experiment

Human behavior is thought to spread through face-to-face social networks, but it is difficult to identify social influence effects in observational studies, and it is unknown whether online social networks operate in the same way. I report results from two randomized trial experiments on political mobilization during the 2010 and 2012 US congressional elections, involving 61M and 120M Facebook users. Alignment with public voting records show that strong social ties are instrumental for political mobilization.