Cable news channels like CNN, Fox, and MSNBC are widely understood to have political leanings, but a new study published in the Proceedings of the National Academy of Sciences surveyed a decade of cable news to measure that bias on a granular scale—by the day, the week, and even the hour. It found that all three networks became more polarized over the period studied—particularly following the 2016 election—becoming more out of sync, with Fox moving to the right in response to events that caused MSNBC and CNN to move to the left.
“There has always been this assumption that media bias is fairly fixed,” says Yphtach Lelkes, co-author on the study and an associate professor at the Annenberg School for Communication, “just ‘Fox News is the right. And MSNBC is the left.’ But what we see is that it moves, and pretty quickly.”
Lelkes and his colleagues focused on one form of media bias for their study: visibility bias. For example, if the majority of guests on a news channel are considered liberal, then the channel itself would be seen as liberal. They analyzed thousands of hours of CNN, Fox, and MSNBC to figure out who appeared on screen during news shows on these channels for at least 10 hours total between January 2010 and August 2020.
“If a person donates to Ted Cruz and Donald Trump, they’re assigned a media bias score based on their financial contributions to political candidates and organizations considered more conservative,” Lelkes says. “And if they donate to Barack Obama and Hillary Clinton, they’re more liberal. So when we identify people on screen, we can also identify their ideology.”
This story is by Hailey Reissman. Read more at Annenberg School for Communication.