Truth decayFacebook's Ad Delivery System Deepens the U.S. Political Divide

Published 12 December 2019

Facebook is wielding significant power over political discourse in the United States, thanks to an ad delivery system that reinforces political polarization among users, according to new research. The study shows for the first time that Facebook delivers political ads to its users based on the content of those ads and the information the media company has on its users—and not necessarily based on the audience intended by the advertiser.

Facebook is wielding significant power over political discourse in the United States, thanks to an ad delivery system that reinforces political polarization among users, according to new research from a team of computer scientists.

The study, published this week by researchers from Northeastern University, the University of Southern California, and the nonprofit technology organization Upturn, shows for the first time that Facebook delivers political ads to its users based on the content of those ads and the information the media company has on its users—and not necessarily based on the audience intended by the advertiser.

“We found that Facebook will disproportionately deliver an ad to the users who [Facebook] believes agree with the ad, based only on the content,” says Alan Mislove, a professor of computer science at Northeastern and one of the authors of the paper. 

Mislove says the findings have grave consequences for democracy in the U.S. Facebook is one of the world’s largest advertising platforms, and its ad delivery system is creating information filter bubbles for its users, the research shows. It reveals that citizens are being served ads that reinforce their existing political beliefs, and being excluded from seeing ads that challenge those beliefs.

In a statement to theWashington Post, a spokesman for Facebook disputed the gravity of the findings.

“Findings showing that ads about a presidential candidate are being delivered to people in their political party should not come as a surprise,” Facebook spokesman Joe Osborne told the Post. “Ads should be relevant to the people who see them. It’s always the case that campaigns can reach the audiences they want with the right targeting, objective, and spend.” 

But Mislove says this is an oversimplification. 

“I don’t think most people understand the level of optimization that’s taking place in online advertising,” he says. “When Facebook is optimizing ads for relevance, they’re also optimizing for Facebook’s profit margin.” 

Facebook, like many of the biggest digital companies, keeps its algorithms under lock and key. So, in order to understand how advertisements are delivered to users, Mislove and his colleagues—a team that also included Northeastern doctoral candidates Muhammad Ali and Piotr Sapiezynski—posed as political advertisers.

Northeastern says thatthe researchers spent more than $13,000 on a set of advertising campaigns that they used to test how Facebook promotes political messaging.