Who are America’s media powers today? The election has put that question at the center of the news, but the answer applies far more broadly. For any leader in any field, understanding today’s most influential media players is crucial. Call them the new ‘Powers That Be,’ after the title of David Halberstam’s 1979 book analyzing that era’s most influential media players: CBS, the New York Times, Time magazine, the Washington Post, and the Los Angeles Times. The new Powers are entirely different, however, and they number just two: Facebook and Google.

They’re in the news over speculation that “fake news” spread via Facebook posts could have influenced the election outcome, and over Google’s high placement of a search result reporting wrongly that Donald Trump got more popular votes than Hillary Clinton. The larger issue is that it’s now possible to hold a serious, legitimate debate on whether these two sites wield excessive influence over hundreds of millions–or perhaps billions–of people worldwide.

Some 44% of U.S. adults get news from Facebook fb , says recent research from Pew. No other site comes close to that; YouTube ranks second with 10% of U.S. adults, followed by Twitter with 9%. It would appear that more Americans get at least some news from Facebook than from any other individual source. Back in 1979, none of the old powers that be, except maybe CBS, could have approached Facebook’s reach today, and none of them could approach it now.

What users see on Facebook is highly influential. One of the company’s own studies from 2012 found that “I voted” posts orchestrated by the researchers influenced an estimated 280,000 additional people to vote in the 2010 midterm elections. The researchers were careful to make their experiment nonpartisan, but it’s easy to imagine how partisans of any cause could launch similarly powerful efforts.

That’s especially significant in light of today’s concerns that many Facebook users are in a “filter bubble” that exposes them mostly to people with views like their own. Separate work by Wellesley University researchers details dozens of past efforts to influence Google search results and Facebook news feeds. The companies constantly try to shut down such efforts, but they’re inevitably always a step behind.

 

Facebook and Google googl hold extraordinary power in another way. At least 75% of all the growth in U.S. online advertising this year will accrue to those two companies; some estimates say 90%. Emarketer forecasts that digital ads will be the largest category of all advertising as of next year. None of the old powers that be ever dreamed of such dominance.

Both companies insist that they’re not media companies—they don’t want to be—and by traditional standards they aren’t. They don’t employ thousands of reporters (or any reporters). But in today’s world they are indeed media companies because that’s how people use them.

In the recent controversy, Facebook CEO Mark Zuckerberg posted that “We must be extremely cautious about becoming arbiters of truth ourselves.” But the reality that all leaders must confront is that being influential today requires competing for attention in the online realms of Facebook and Google, today’s towering kings of media.

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