A new study by a UC San Diego political science professor published in Nature examined the impact of a non-partisan voter engagement campaign run by Facebook to encourage participation of in the 2010 elections. More than 60 million people on Facebook saw a non-partisan “get out the vote” message at the top of their news feeds on Nov. 2, 2010.

The message featured a reminder that “Today is Election Day”; a clickable “I Voted” button; a link to local polling places; a counter displaying how many Facebook users had already reported voting; and up to six profile pictures of users’ own Facebook friends who had reported voting.

According to the study, about one third of a million more people showed up at the ballot box in the United States in 2010 because of this single Facebook message on Election Day.

“Social influence made all the difference in political mobilization,” [UCSD Political Science Professor James] Fowler said. “It’s not the ‘I Voted’ button, or the lapel sticker we’ve all seen, that gets out the vote. It’s the person attached to it.”

The researchers estimate that the direct effect of the Facebook social message on users who saw it generated an additional 60,000 votes in 2010. But the effects of the social network – of social contagion among friends – they say, yielded another 280,000 more, for a total of 340,000. In other words, Fowler said, the social network yielded an additional four voters for every one voter that was directly mobilized.

The researchers did not find any evidence of differences in effects among self-described liberals and conservatives. Research is now continuing on what kinds of messages work best for increasing voter participation and what kinds of people are most influential in the process.

Although the effect of the message per friend was small, Fowler points to the advantages of scale. When you multiply a small effect across the millions of users and billions of friendships in online social networks, you quickly get to numbers that make a difference.

“The main driver of behavior change is not the message – it’s the vast social network. Whether we want to get out the vote or improve public health, we should not only focus on the direct effect of an intervention, but also on the indirect effect as it spreads from person to person to person.”

Click for a summary of the UCSD Study and additional information on the findings from UCSD.edu.