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Here is the central tenet of Facebook’s business: If lots of people click on, comment on, or share an ad, Facebook charges that advertiser less money to reach people. The platform is a brawl for user attention, and Facebook sees a more engaging ad as a better ad, which should be shown to more users.

This has been true for years. No one inside or outside Facebook has ever hidden this fact. All the dynamics of the News Feed—most classed under the rubric of “clickbait”—also exist in paid advertising, but success (or failure) is denominated in dollars.

And yet, in the context of the 2016 Presidential Election, this way of auctioning advertising—originally developed by Google and normalized in the pre-Trump age—can seem strange, unfair, and possibly even against the rules that govern election advertising.

In a new essay at Wired, the former Facebook advertising staffer Antonio García Martínez lays out what is undoubtedly true: Trump’s ads had far higher engagement rates, which meant he paid less to reach a given number of people.

“A canny marketer with really engaging (or outraging) content can goose their effective purchasing power at the ads auction, piggybacking on Facebook’s estimation of their clickbaitiness to win many more auctions (for the same or less money) than an unengaging competitor,” García Martínez writes.

Trump, of course, was the canny marketer, while Clinton’s team was the unengaging competitor. While most everyone covering the digital portion of the election has known this, the logical conclusion that follows can still feel startling.

During the run-up to the election, the Trump and Clinton campaigns bid ruthlessly for the same online real estate in front of the same swing-state voters. But because Trump used provocative content to stoke social-media buzz, and he was better able to drive likes, comments, and shares than Clinton, his bids received a boost from Facebook’s click model, effectively winning him more media for less money,” García Martínez continues. “In essence, Clinton was paying Manhattan prices for the square footage on your smartphone’s screen, while Trump was paying Detroit prices. Facebook users in swing states who felt Trump had taken over their news feeds may not have been hallucinating.”

After the article was published, one of Trump’s campaign staffers, Brad Parscale, posted a link to it and tweeted a chest-pounding follow-up. “I bet we were 100x to 200x [Clinton],” he wrote. “We had CPMs [cost per thousand impressions] that were pennies in some cases. This is why @realDonaldTrump was a perfect candidate for Facebook.”

No one has the precise numbers for how much more engaging Trump’s ads were or how much less money he paid to reach people than Hillary Clinton. But it’s clear that Donald Trump—aided by bots and this advertising boost—far outstripped Clinton in overall engagement. Mark Zuckerberg pointed this out back in November of 2016.

For example, during two months in the run-up to the election that the data journalist Kate Stohr looked at overall interactions (likes, comments, shares), Trump had almost three times Clinton’s engagement, 36 million to 12 million. Of the two months in the dataset, Clinton’s total interactions only topped Trump’s on three days.

Trump was a socialgenic candidate with a team that maximized—or exploited—his potential to create engagement: As dozens of stories have attested over the last two years, Trump was the “clickbait candidate.” Clinton’s posts and advertisements, for whatever basket of reasons, did not generate the same volume of likes, clicks, and shares. And in today’s electioneering, that has severe consequences.

While this much has been known, García Martínez’s logical conclusion that this means there was an ad-pricing differential seems to have hit a nerve. That’s because FCC election regulations require that candidates be charged equal rates. “The rates, if any, charged all such candidates for the same office shall be uniform and shall not be rebated by any means, direct or indirect,” the regulation states.

The FCC promulgated this regulation to cover broadcasting, but on its face, it would seem to present questions not just for Facebook, but for any auction-based advertising platform such as Google’s, Twitter’s, and various ad networks.

The fact that ad-auction platforms all basically work like this has led some people in digital marketing to wave off the FCC argument. “This article is nonsense and more clickbait,” tweeted Tim Lim, a digital-ad consultant who works with Democrats. “Advertisers buy inventory on demand and/or based on performance (CPC, etc), so costs set on their terms. Same approach is used by @Google, @nytimes, and slew of other platforms.”

From Facebook’s perspective, their platform is “neutral,” in the sense that it provides all advertisers with an equal opportunity to maximize their reach and minimize their costs. “The auction system works the same for everybody,” says Andy Stone, a Facebook spokesperson. “It affords equality of opportunity.”

While people in the field understand that this is how the game is played, others outside digital marketing are discomfited by these changes in the world. The social-media consultant Andréa López compared the slow-motion realization to the time after the mortgage meltdown, when the workings of mortgage-backed securities and other banking procedures suddenly seemed suspect in the light of the problems the industry encountered. “It’s kind of like [the] 2007-8 finance-meltdown daze phase of processing how banks work,” she told me.

Some less hinged responses accused Facebook of wanting Trump to be elected because of the Russian investor Yuri Milner or the right-wing board member Peter Thiel. But most evidence suggests that the vast majority of Facebook employees are just regular slightly left of center technocrats who were rooting for Hillary Clinton.

Their personal politics mattered far less than the politics of the system that they half-wittingly created. While the clickbait candidate this last round was Donald Trump, future elections could just as easily feature a left-wing ideologue with an equally engaging style.

The University of Virginia media-studies professor Siva Vaidhyanathan, who has a book coming out on Facebook in September—Antisocial Media: How Facebook Disconnects Us and Undermines Democracy—had a stark response, especially with the midterms six months away. “There is no reform. The problem with Facebook is Facebook,” he told me. “When you marry a friction-free social network of 2 billion people to a powerful, precise, cheap ad system that runs on user profiling you get this mess. And no one can switch it off. So we are screwed.”

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