While it has presented itself as "balanced" over the years, there's little doubt that Fox News has consistently supported Republican candidates and positions even when that required taking an editorial position against basic facts . On some level, this has worked, as surveys have indicated Fox viewers are more likely to get those same facts wrong. But is it working in terms of the larger goal of supporting Republican causes?

According to a new study, the answer is yes. Two researchers, Gregory Martin and Ali Yurukoglu, have taken advantage of huge amounts of public data, some inadvertent experiments, and a lot of previous research to look into the influence of Fox News on people's votes. They conclude that, in recent elections, the mere availability of Fox could shift nationwide votes by over a percentage point.

The paper itself is rather complicated and tackles a lot of related issues regarding the influence of news media on voting. Martin and Yurukoglu are quite fond of mathematical analysis; it's rare for them to go more than a paragraph without regressing something (often several somethings). As a result, a lot of the paper reads like the following: "If voters treat signals from slanted outlets as true draws on the state of the world, and further, if they do not account for the correlation between repeated signals from the same source as in the model of DeMarzo, Vayanos, and Zwiebel, then equation 8 arises as the inverse-variance-weighted average of signals observed by viewer i in period t."

That said, the basic details of their argument are pretty straightforward, provided you break out the individual analyses.

Are our cable news sources biased?

This may seem like a formality, but the authors went and tackled it anyway, using methods that had been developed by other researchers. The analysis relied on digitized transcripts of speeches and statements from members of Congress. This allowed the researchers to identify phrases frequently used by members of one of the two parties during the 2000, 2004, and 2008 elections.

Many of these are about what you'd expect. The Democrats frequently mention civil rights, while Republicans are fond of saying "Reagan." In some cases, the party involved was the opposite of what you might expect. For example, the Democrats were the ones talking about "Republican leadership" and the "Bush administration," presumably because they were criticizing it. There was only one term, however, that appeared to be part of a political talking point, that being the Republicans' terming the estate tax as a "death tax."

Thus, the analysis didn't measure whether a news channel was parroting a party's talking points. Instead, it was looking at how often a station was mentioning what a given party was talking about.

For most of the period analyzed, CNN was indistinguishable from neutral (it saw a slight tilt toward Democrats during the 2010 midterm elections). MSNBC was also quite neutral up until midway through the last decade, at which point its management made a strategic lurch toward the Democrats. Since this happened late in the study and MSNBC's viewership is relatively small, the authors were never able to find an effect of viewing this channel that was statistically distinguishable from zero.

And then there's Fox. Fox started out with a slight tendency to talk more about what Republicans were saying, but that tendency grew dramatically more pronounced around Obama's election. (The dramatic shift with Obama's election is probably worth a separate study on its own.) It remained more polarized than MSNBC right up until the end of the study period in 2012, when MSNBC finally caught up with it. In fact, the authors' analysis suggests that Fox is teetering on the edge of being so relentlessly Republican that it risks losing business by driving any liberal viewers away.

Does this influence voters?

Most people would assume that news viewers would self-select a news source that matches their ideology. But various surveys have indicated that's not true, and the authors have a clever way of showing it's not the case here. It basically relies on people's laziness. On startup, most set-top boxes will simply default to the lowest channel number; if people are surfing, they'll surf upward from there. Not surprisingly, many viewers have a tendency to stop at lower-numbered channels.

For cable TV providers, channel number assignments are largely the result of historic accident. Thus, whether a person is more likely to watch Fox, CNN, or MSNBC depends in part on the order they appear on the channel list. Thus, if Fox is the lowest-numbered channel in a given region, people will be slightly more likely to watch it. The control, in this case, comes in the form of the US' two satellite TV providers, which offer the same channel lineup nationwide. "A one-standard-deviation decrease in Fox News’s channel position," they calculate, "is associated with an increase of approximately 2.5 minutes per week in time spent watching Fox News."

Combined with the data above, this means that in certain cable markets, people tend to get exposed to more Fox News, which means more exposure to Republican ideas. At least within this study period, there was no effective counterbalance, either. CNN was too neutral, and MSNBC's influence was too small.

Is that enough to sway the vote? Here, Martin and Yurukoglu have a couple of ways of getting at the issue, based on ZIP-code-level voting and census data. For example, they could compare votes during the study period to those that occurred earlier, prior to the advent of Fox News. They could also predict the voting behavior of each ZIP code to the votes predicted by the demographics.

The results are rather striking. Channel position alone, assigned randomly, increased voting for Republican presidential candidates by 0.3 percentage points. And remember, channel position only induces an average of an extra 2.5 minutes of viewing a week. (Of course, that likely means that a smaller number of people watched a lot more than 2.5 minutes.)

The effect of Fox News overall, which has an audience that includes lots of people who watch it intentionally, is even larger. "We estimate that removing Fox News from cable television during the 2000 election cycle would have reduced the overall Republican presidential vote share by 0.46 percentage points," the authors conclude. "The predicted effect increases in 2004 and 2008 to 3.59 and 6.34 percentage points, respectively. This increase is driven by increasing viewership on Fox News as well as an increasingly conservative slant."

It shouldn't be surprising that a very popular TV channel that broadcasts a very consistent ideological message would have an influence on public opinion. The numbers for the 2008 election, however, seem remarkably high. But there's no difference in the methods used to obtain those numbers compared to the analysis done on the earlier elections, which produced more reasonable looking numbers. And those methods are quite clever, providing ways of turning a historical accident—the location of TV channels—into a controlled experiment.

American Economic Review, 2017. DOI: 10.1257/aer.20160812 (About DOIs).