There are now more than 100 million customers around the world who are members of Amazon’s Prime Loyalty program, founder and chief executive Jeff Bezos has revealed for the first time.

Bezos, who disclosed the figure in his annual letter to Amazon shareholders, has traditionally kept the scale of Amazon Prime private, but the nine-figure milestone appears to have changed his mind.

Prime, which charges customers an annual fee for a variety of services like free delivery and video streaming, expanded into Mexica, Singapore, the Netherlands and Luxembourg in 2017 and will expand into Australia in 2018.

In his 2018 letter Bezos provided an update on 16 of Amazon’s distinct business areas, reporting growth on all fronts as the e-commerce giant prepares to report March quarter earnings later this month.

Highlights included selling tens of millions of echo devices in 2017, doubling the membership of Amazon Music over the last six months, reducing prices at Whole Foods, and the launch of fashion offering Prime Wardrobe.

Bezos used the first half of his letter to outline the importance of high-standards in the never-ending pursuit of satisfying the “divinely discontent” customer.

“One thing I love about customers is that they are divinely discontent. Their expectations are never static – they go up. It’s human nature. We didn’t ascend from our hunter-gatherer days by being satisfied. People have a voracious appetite for a better way, and yesterday’s ‘wow’ quickly becomes today’s ‘ordinary’,” Bezos said.

“How do you stay ahead of ever-rising customer expectations? There’s no single way to do it – it’s a combination of many things. But high standards (widely deployed and at all levels of detail) are certainly a big part of it.”

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