Cable news networks becoming even more politically polarized, study says

PHILADELPHIA — Cable news programs can hold incredible sway over the American public. As of early 2020, Nielsen estimates the average American adult watches nine and half hours of cable news on a weekly basis. While it's no secret that certain channels lean one way or the other on the political spectrum, researchers from the University of Pennsylvania find three of the biggest became increasingly more polarized between 2010 and 2020.

Study authors analyzed a decade's worth of news programs on Fox, MSNBC, and CNN in an attempt to measure mounting political bias on a granular scale (by the day, the week, and the hour). All three networks steadily became more polarized during that period, especially directly after the 2016 presidential election. These trends moved more or less in sync with one another; when one event caused Fox to move further to the political right, that same event usually pushed MSNBC and CNN to move to the left.

“There has always been this assumption that media bias is fairly fixed,” says study co-author Yphtach Lelkes, an associate professor at the University of Pennsylvania’s Annenberg School for Communication, in a media release. “Just ‘Fox News is the right. And MSNBC is the left.’ But what we see is that it moves, and pretty quickly.”

What you see is what you get

The research team focused specifically on one particular form of media bias: visibility bias. This type of bias is straightforward. For example, if most of the guests on a new channel are liberal, then researchers deemed that channel as liberal. Study authors viewed and analyzed thousands of hours of CNN, Fox, and MSNBC to track who appeared on screen during various news programs on the three channels for a minimum of 10 hours total between January 2010 and August 2020.

They assigned each guest a media bias score based on financial contributions to political candidates and organizations according to Stanford University’s Database on Ideology, Money in Politics, and Elections (DIME).

“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,” Prof. Lelkes explains. “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.”

The research team believes these bias scores are compelling evidence that between 2010 and 2020 Fox moved much further to the political right, while CNN and MSNBC moved further to the left.

“For many years, Fox News was to the right of MSNBC and CNN,” Prof. Lelkes adds, “but they used to track each other. When Fox moved to the right, so did MSNBC and CNN. They all flowed together. After Trump came into office, they responded to events in the news by leaning away from each other and more strongly toward their respective ideologies.”

Primetime polarization

The political divide between channels becomes even more pronounced when the study narrowed its scope down to primetime programming. In comparison to other shows on their respective networks, primetime news programs like “Anderson Cooper 360” on CNN and “The Rachel Maddow Show” on MSNBC skew more sharply to the far left. Similarly, “Tucker Carlson Tonight” on Fox leans heavily to the far right.

“We don't really see that dramatic polarization for the morning and afternoon shows,” Prof. Lelkes concludes, “which are more hard news, more fact-based shows.”

On a related note, another recent study conducted at UPenn reveals that Americans who primarily get their news from television (as opposed to online) are much more likely to only watch channels that reflect their beliefs, essentially keeping themselves in a “partisan bubble.”

All in all, both of these projects certainly don't convey a positive picture of American politics. Viewers seem more content than ever to only hear what they already agree with, and news channels are happy to provide just that.

The study is published in the Proceedings of the National Academy of Sciences.