For years, this has been one of Amazon’s biggest secrets: how many people pay for the Prime membership.

A big round number appears to have prompted CEO Jeff Bezos to finally lift the veil: “13 years post-launch, we have exceeded 100 million paid Prime members globally,” he wrote in this year’s letter to shareholders.

He added that in 2017, more new members joined Prime than in any other year. The membership generally costs $99 a year in the U.S. and lures people in with free two-day shipping and access to video and music streaming. Last year and earlier this year, Amazon added discounted Prime rates for recipients of Medicaid and government assistance programs.

Prime subscribers are known to be more lucrative to Amazon, estimated to spend twice as much money every year than non-members, according to Consumer Intelligence Research Partners. Analysts have been projecting the number of Amazon’s paid subscribers as around 65 million to 85 million, while the company had historically just referred to “tens of millions.”

In a letter to shareholders released in 2016, Bezos wrote: “We want Prime to be such a good value, you’d be irresponsible not to be a member.”

Annual letters from Bezos to shareholders are a popular read in the business world. In this year’s note, he muses about the value of setting the highest standards (“I believe high standards are teachable”), the art of great memos (“They simply can’t be done in a day or two”) and the human nature of ever-rising customer expectations (“We didn’t ascend from our hunter-gatherer days by being satisfied”).

Wednesday’s letter, in running through Amazon’s recent milestones, highlights the sheer scope of the company’s reach: its massive cloud-server business, smart assistant Alexa and the Alexa-powered home devices, award-winning TV and movie production, streaming deals with cable and TV networks, a recent push into fashion, the launch of a cashierless store in Seattle and the blockbuster $14 billion acquisition of Whole Foods.

Not mentioned were Amazon’s relatively nascent push into home security with the purchase of smart-doorbell maker Ring and the company’s for-now vague plans in health care, which had spooked the industry. In Wednesday’s letter, Bezos said Amazon employs more than 560,000 globally.

Amazon has also dramatically grown the number of small businesses and other third-party sellers who compete alongside Amazon’s own retail business on the shopping platform. In the letter, Bezos said 2017 marked the first year when more than half of the goods sold on Amazon worldwide were from third-party sellers.

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