With more people turning to mobile devices and other portable screens when breaking news erupts, how important are TV ratings for the cable-news networks?

At present, the answer is "plenty," with Fox News Channel dominating the arena. But other screens may soon take news viewers' attention to other areas. "The rapid growth of mobile is a key factor driving the move to digital news," according to Pew Research Center's 2013 edition of its "State of the News Media" report. "Indeed, the proliferation of devices is giving rise to a new multiplatform news consumer, one who accesses news through a combination of different devices and traditional sources."

According to Pew, "fully 64% of tablet owners say they get news on their devices weekly and 37% report they do so daily." As things turn out, the trend is quite similar for people who own smartphones. Pew found 62% get news on their device weekly and 36% do so daily.

Surges are already taking place. In October, Fox News Mobile saw the number of unique visitors for browser access alone increase by 75% over the year-earlier period, and 18.2% over September, according to data from comScore. Unique visitors by application access grew 59% over the year-earlier period and 16% over September.

With that in mind, audience interaction with the news outlets' various digital outposts bears watching. In October, for example, Nielsen found smartphone apps and mobile sites related to CNN's Digital Networks amassed 27.9 million unique users, compared with 16.3 million for Yahoo-ABC News sites, 13.8 million for Huffington Post, 10.78 million for the Fox News Digital Network, 10.76 million for USAToday.com, 10.14 million for the NBC News Digital Network, and 9.03 million for the CBS News Network.

When it comes to the amount of time users spent with each, Nielsen determined a different pecking order. Readers of the New York Times spent an average of 54 minutes-plus with the mobile sites during the month, while CNN aficionados spent more than 33 minutes in October. Readers of USAToday.com spent an average of 25 minutes and 15 seconds while Fox News Digital Network captured readers for an average of 20 minutes and 7 seconds during the month. Readers of NBC News Digital spent an average of 14 minutes and 39 seconds. Other news outlets kept readers during the month for six minutes or less.

The numbers may play a bigger role in how some of the nation's most recognizeable news brands are perceived in years to come. As smartphone ownership rises, so too, one suspects, will the behavior of seeking out news content from digital venues first, and TV secondarily. Already, CNN has vowed to increase its emphasis on consumers who get its content from mobile phones and tablets. The Time Warner network has invested at least $15 million 2013 to rework its digital infrastructure to make the placement of news content and advertising across different digital outlets easier.

News junkies likely make decisions about where to get their information based on a strange calculus of breaking-news alerts, mobile access, and more. Even happenstance may nudge a decision. So Jeff Malmad, who heads the mobile practice at MindShare North America, a large media-buying shop that is part of global ad company WPP, likes to dig deeper when choosing where to place his clients' commercials on news-outlet mobile sites.

"There's a whole host of data points that I would look to understand where I'm getting the best traction," he said. He examines app stores and looks to understand how long consumers spend at a particular site and what drives them to stick around or split. He also may consider whether he needs the scale of a single media brand or if he can build an audience by buying up inventory across different news sites.

While mobile tells part of the story, traditional Web surfing relates another. For the month of November, comScore found Yahoo-ABC News captured the most unique viewers, nearly 77 million, while CNN lured 65.9 million.

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