A 61-Million-Person Experiment in Social Influence and Political Mobilization.

The authors ran a trial on Facebook using social proof to encourage people to vote during the 2010 U.S. Congressional Elections. Treatment Group 1 contained 60 million people who saw a neutral ‘get out the vote’ ad along with a clickable “I voted” button. Treatment group 2 contained 600,000 people who saw an ad (pictured) embedded with a social proof element showing which of their friends had voted. The Control group contained 600,000 people who received no imploration to vote.The results showed that users who received the social message were more likely to have clicked “I voted”. While Treatment Group 1 and the Control group had the same turnout rates, Treatment group 2, which implemented the social proof mechanism, had significantly more turnout rates. The researchers estimate that the direct effect of the Facebook social message on users who saw it generated an additional 60,000 votes and the effects of the social network – of social contagion among friends – yielded another 280,000 more, for a total of 340,000. In other words the social network yielded an additional four voters for every one voter that was directly mobilized. To verify whether the participants really did vote rather than just claim they the authors compared turnout rates among their treatment & control groups and found 4% of those who said they voted had not.