Watching Fox News makes viewers more likely to vote for Republican presidential candidates, a study conducted by an Emory professor found.

Emory Assistant Professor of Political Science Gregory Martin and Stanford Associate Professor of Economics Ali Yurukoglu estimated in their paper titled “Bias in Cable News: Persuasion and Polarization” that the Fox News Channel was responsible for 0.46 percentage points of the Republican vote share in 2000, 3.59 points in 2004 and 6.34 points in 2008. The paper was published in the September 2017 edition of The American Economic Review.

The researchers calculated that an additional three minutes of Fox News consumption per week over the course of an election season year made a Democrat-identified voter 58 percent more likely to vote for Republican George W. Bush in the 2000 presidential election, 27 percent more likely to vote for Bush again in 2004 and 28 percent more likely to vote for Republican John McCain in 2008.

MSNBC, which is regarded as a more liberal network, had an 8 percent Republican-to-Democrat conversion rate in 2008.

Martin said the reason Fox’s influence on the Republican vote share has increased over time is two-fold: Fox has become increasingly conservative since its founding in 1996, and its audience has grown — ratings have doubled since 2000. Fox was seen by 2.35 million viewers in the first quarter of 2017, compared to 1.64 million for MSNBC and 1.06 million for CNN according to Variety.

Using congressional records, Martin and Yurukoglu identified approximately 1,000 partisan phrases — terms that were almost always used exclusively by either Democrats or Republicans — to quantify how liberal or conservative the networks were over the election season using a mathematical model, according to the paper. For example, the term “death tax” is used almost exclusively by Republicans to describe estate taxes. Equipped with a library of partisan phrases, the researchers searched for relevant phrases in transcripts of programs from cable news networks. The researchers used transcripts from all cable news programs from 1998 to 2012 from Fox, MSNBC and CNN.

Fox has positioned itself farther to the right than is in its financial interest, Martin said.

“If [Fox] were out to maximize [its] viewership, [the network] would want to adopt more centrist positionings, close to what CNN does in practice,” Martin said. “But we find that Fox is actually much closer to the position that would maximize its electoral influence than it is to the position that would maximize its viewership.”

In general, Martin said it’s difficult to study the effects of cable news consumption on consumer behavior because the practice is inherently self-selecting.

“People select into media that confirms their preexisting beliefs,” Martin said. “For example, if you compare the audience of Fox to MSNBC, you’d see that Fox is roughly two-thirds Republican and MSNBC is maybe closer to one-third Republican.”

A large portion of Fox viewers were probably already Republicans before they started watching Fox, Martin added.

To account for that and to isolate the persuasive effect of the network, Martin and Yurukoglu called on research dating as far back as the 1980s that indicates viewers’ tendencies to watch networks with lower channel numbers.

“Initially we started this trying to replicate [a 2007 study] with better data, and then we realized when we got into it that we had this additional variation from the channel position that we could use to do something better,” Martin said.

CBS, NBC and ABC have high ratings and almost always occupy low channel positions. A majority of viewers begin watching programs on low channels, and when their program ends, they “channel surf” upward to higher channels until they find a program they like, Martin explained.

Martin and Yurukoglu compared voting data from geographic locations where Fox News has a lower channel number to areas where Fox News has a higher channel number.

The researchers determined that in regions where Fox News occupies a channel slot roughly one standard deviation (17 channel positions) lower in channel number than average, people watch Fox an average of 2.5 minutes more. That extra consumption is tied to an increase of 0.3 points in the Republican vote share in presidential elections.

Martin said the magnitude of Fox’s influence is larger than he expected. He was also struck by the amount of  viewers suggestible to change their vote based on news coverage.

“There [is] a significant number of people that tune in close to the election who haven’t really made up their minds or don’t follow politics closely, and those people are more persuadable than I would’ve thought,” Martin said.

Fox News did not respond to request for comment.

Richard Chess contributed reporting.