This chart shows just how much Facebook, Google and Amazon dominate the digital economy

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Mark Zuckerberg, Sundar Pichai, and Jeff Bezos.

• The chart below shows the amount of power that three of the biggest tech companies have in key sectors of the digital economy.
• 2 out of every 3 digital ad dollars in the US goes to Facebook, Google or Amazon, according to eMarketer data.
• Tech companies have long argued that competition is just one click away in internet market, but the concentration of power in certain markets is now under renewed scrutiny by regulators, politicians and the public.
• Visit Business Insider's homepage for more stories.

There's a lot of money to be made in the digital economy. And right now, a lot of that money is flowing into the coffers of three companies in particular.

Google, Facebook and Amazon are among the most valuable tech companies in the world. And as shown in this chart, based on data from eMarketer, the three companies utterly dominate certain segments of the online economy in the US. (Axel Springer, Business Insider's parent company, also owns eMarketer.)

More than two of out every three dollars spent on digital ads in the US goes to one of the three companies., for instance. Facebook, not surprisingly, takes the lion's share of social media advertising, and it's closing the gap with Google on mobile ads.

With calls to rein in the power of the big tech companies, and some like Senator Elizabeth Warren even saying it's time to break up some of these corporations, the market share figures below represent something of an inconvenient truth - no matter what the companies may say about competition being "just a click away."

Olivia Reaney/Business Insider

Amazon is a growing power in digital advertising, but its real stronghold remains its online retail business, with 37.7% of all e-commerce sales in the US ringing up at the Amazon cash register. Notably, that number is actually the result of a downward revision by eMarketer following new information about Amazon's third-party sales- the research firm had previously estimated Amazon's share of the US e-commerce market was 47%.

As the TV industry gets upended by the internet, Google and Amazon are also positioned to benefit from new revenue streams. Nearly 27% of consumers who watch streaming video on a TV screen in the US watch through Amazon, while nearly 17% watch through a Google service or device. Note that the estimates for "over-the-top" TV viewers, which refers to video delivered over the internet independent of a traditional TV service, is above 100% due to overlap of consumers using more than one service.

• Read more about Big Tech's market power and the calls to rein it in:
• Here's why the failed attempt to break up Microsoft will make or break the crackdown on Facebook, Amazon, and Google, according to 2 top lawyers in the Microsoft case
• Elizabeth Warren's campaign posted a billboard calling for the breakup of Big Tech in the heart of the tech industry
• Trump drops the biggest hint yet that he's coming after the big-tech 'monopoly' with potential billion-dollar fines
• Here's what could happen to Google and its $137 billion business empire if it loses the antitrust battle