The latest figures from the Interactive Advertising Bureau show that the third quarter last year was the biggest ever, with a total of $17.6 billion spent on digital ads. That’s a 20% increase from the same period a year earlier, thanks to growth in mobile and video. This growth “reflects marketers’ trust in the internet’s power to connect with today’s audiences,” the IAB said.

If you look beneath the surface, however, it also reflects the fact that a majority of those audiences are controlled by Google (GOOG) and Facebook (FB)—and if anything, their control is accelerating.

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Last year, Pivotal Research analyst Brian Wieser estimated that digital advertising revenue in 2015 also soared by 20% from the previous year to a record of $60 billion. Close to 65% of that went to Google and Facebook, he said, with the search giant taking $30 billion and Facebook taking $8 billion.

“Smaller companies will continue to operate in the shadows of the industry’s two dominant players,” Wieser told investors in a research note at the time.

Halfway through last year, Jason Kint of the advertising trade group Digital Content Next looked at the total ad revenue booked by those two companies as a proportion of the overall industry, and found that they accounted for about 90% of all the growth in the business.

Last week, Kint updated those figures, and the picture they paint has become even more bleak. Based on the IAB’s numbers and public financial numbers from Google and Facebook, the two digital giants accounted for about 99% of the $2.9 billion in advertising growth in the third quarter—with Google making up about 54% of the total and Facebook about 45%, leaving just 1% for everyone else.

updated duopoly #s. new IAB data came out yesterday. easy to run vs earnings for goog and fb, it's evident everyone else is zero sum game. pic.twitter.com/wolgdpfcxp

— Jason Kint (@jason_kint) December 30, 2016

This duopoly control has had an increasing impact on the advertising-tech market as well, something that used to be a growth area both for publishers and for ad networks. According to a recent analysis by the Financial Times, both the number of financing deals and the amount raised by ad-tech companies has declined sharply in the past year.

The number of ad-tech companies raising money dropped 17% last year compared with the year earlier, data from CBInsights shows, and the total volume of funding fell 33% to $2.2 billion from $3.2 billion, putting it back where it was in 2013.

“Ad tech’s struggle as a sector is absolutely to do with the dominance of Facebook and Google,” Balderton Capital venture partner Suranga Chandratillake told the FT. “Ultimately advertising is about selling attention, and if most of that attention is focused on Google and Facebook, then naturally they can monetize it.” He added:

“Even if you manage to build a sustainable advantage for a few years, how do you scale to compete with Google or Facebook? That’s why traditional adtech does feel dead from a venture perspective.”

In a recent interview with ad industry veteran Jay Sears, Pivotal’s Wieser said the digital-media industry has effectively become a giant duopoly in which Google and Facebook win almost everything, advertisers have to play by their rules, and other media companies “fight for the scraps.”

New York-based venture investor Fred Wilson, meanwhile, predicted in a forecast for 2017 that “the ad:tech market will go the way of search, social, and mobile as investors and entrepreneurs concede that Google and Facebook have won and everyone else has lost.” It will be nearly impossible to raise money for an online advertising business in 2017.”

This is how modern political advertising works:

In the past, digital advertising may have been seen as an add-on or supplement to traditional advertising markets, but that is no longer the case. According to estimates from eMarketer, spending on digital ads in the U.S. will likely grow this year to the point where it is larger than the amount spent on television, the former Goliath of the industry.

Data on users and their preferences and behavior is the Holy Grail for most advertisers, and the reality is that Google and Facebook have orders of magnitude more data than their nearest competitors, and more ways to slice and dice it.

In the case of Facebook, the company has more than 1.5 billion users—far more than any other single media business commands—and it tracks what they see and click on in ways that most media companies can only dream of. And that means advertisers will continue to work with them even when they admit that their data was wrong, as Facebook has several times.

Twitter and Snapchat are trying to compete on the same playing field as Google and Facebook, but both remain bit players so far. So is the future for media companies simply one of deciding which of two giant walled gardens they wish to build a majority of their business on, or pay rent to? For the moment, at least, that appears to be the case.