The political bias of cable news shows is surprisingly dynamic, according to new research investigating the average partisan leans of cable news channels over time.

Using a method to measure average political leanings, University of Utah political scientist Josh McCrain and colleagues found that even on channels that are well-known for a particular political bias, the strength of that bias can change from hour to hour and from show to show. They also found that the current polarization of cable news channels may be driven by the leanings of the primetime shows.

“This potentially tells us a lot about the cable news marketplace and how they compete for viewers,” McCrain says. “It’s not necessarily about quality of reporting or programming variety, but about the slant of their primetime programs.”

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

TV is more than static

If asked about the political biases of news channels Fox News and MSNBC, many might readily say that Fox News leans conservative and MSNBC leans liberal, and that it has been so as long as they can remember. Political scientists and economists, in their studies of cable news, have typically assumed that the biases of news outlets are static.

“I think, largely, this is because it makes a lot of our work easier if we assume it’s static,” McCrain says. “If anything, I think researchers might have assumed it did not change much. We show it’s actually quite a bit more interesting than that static positioning, and it depends a lot on the time of day and the specific show.”

McCrain and his colleagues, Eunji Kim of Columbia University and Yphtach Lelkes of the University of Pennsylvania, set out to measure media bias in cable news shows over a decade, looking for ways to quantify how bias has changed over time.

Quantifying bias

How do you come up with a quantifiable measure of a channel’s political slant? McCrain and his colleagues took a novel approach, aided by a singular tool: the Stanford Cable News Analyzer, which contains a repository of data on what cable news is talking about and who shows up onscreen, dating back to 2010. Users can search for particular people or words and get a graph of the frequency of mentions over time along with clips that mention the search term. “We owe them a bunch of credit for their work,” McCrain says.

The researchers utilized the Stanford Cable News Analyzer’s facial recognition feature to quantify how much an individual’s face appears on screen. The idea, sometimes called “visibility bias,” is that if an outlet is more likely to feature political actors from the left than from the right, then the outlet is likely slanted more liberal. With the Stanford team’s cooperation, McCrain and his colleagues tabulated individuals’ screen time by channel by day, show and time of day.

Using another Stanford-created database, the Database on Ideology, Money in Politics, and Elections, the team matched those appearing on cable news with a score of their political ideology, derived from their political donation activity, which is public information.

Let’s take one example: Wayne LaPierre is the CEO of the National Rifle Association. “This is obviously a politically active individual, and someone who donates a lot to Republican candidates,” McCrain says. That donation activity yields a very conservative score for LaPierre.

Once you have all of this data, what can you do with it?

Surprisingly dynamic

McCrain and his colleagues used the political actors’ ideology scores to then look at which channels give screen time to which kind of political actors at different times of day, and then take an average of political bias scores to determine a channel’s leaning. LaPierre, for example, appeared frequently on Fox News shows over the decade of cable news data, influencing that channel’s political score, and more particularly on the Sean Hannity show, influencing that show’s score.

Looking at the results together, the researchers found that the most conservative shows were typically Fox News shows and the most liberal were MSNBC and CNN. Maybe not too surprising.

But over time there’s more variation.

Within a day, cable news shows typically air talk shows in the morning, hard news in the afternoon, and some of their most popular shows in primetime. The results showed that the political lean of all three major cable news channels were most similar in the afternoons, before becoming polarized again in primetime.

“We also find that shows tend to shift and evolve over time,” McCrain says. “For instance, The Rachel Maddow Show and The O’Reilly Factor looked similar in visibility bias during Obama’s first term. However, as 2016 approached, they began to diverge, with Maddow becoming one of the most liberal shows on MSNBC and O’Reilly one of the most conservative on Fox.”

Primetime

Post-2016, the political bias of the news channels polarizes sharply. McCrain and his colleagues write that the polarization is largely driven by the primetime shows.  

“Primetime is where these channels make their money,” he says. “Viewership is highest, and they directly compete with each other for eyeballs.” So emphasizing certain political leanings, he adds, may show how the channel believes it can increase its revenue.

Questions about the relationship between political bias and viewership have important downstream implications for voters and democracy, McCrain says.

“Research shows that exposure to partisan media can shift election outcomes, and once people are exposed, they continue to seek it out. Our finding that media bias is dynamic and, potentially, a product of competition between channels, helps us better understand what generates partisan media bias and why it proliferates.”

Find the full study here.