The online retail giant debuted Prime 13 years ago as a way for people to get free two-day shipping and access to the company’s video streaming library.

In the past, Amazon has only disclosed vague information about the number of Prime subscribers, such as it having “tens of millions of members.” The updated number highlights the growth of the company’s subscription service, which Amazon has pushed heavily over the years as a way to retain customers that in turn fuel its core retail business with each purchase. Still, Amazon stopped short of full disclosure of its Prime subscriber service, like how much revenue it generates.

In addition to membership numbers, Bezos said in a letter to shareholders that the company had shipped over 5 billion items in 2017 as part of its Prime service and that “more new members joined Prime than in any previous year.” However, he didn’t say how many people signed up in past years.

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Bezos also bragged about Amazon’s recent marketing campaigns, including its Prime Day event in July. He said that the company’s Prime Day for 2017 was its “biggest global shopping event ever” until it was soon eclipsed by Cyber Monday, the day of online shopping deals following the Thanksgiving holiday weekend.

“Prime Day 2017 was our biggest global shopping event ever (until surpassed by Cyber Monday), with more new Prime members joining Prime than any other day in our history,” he said.

As for sales of some of Amazon’s other heavily promoted products and services, Bezos remained typically vague.

Amazon sold “tens of millions” of its Internet-connected Echo speaker; its online streaming music service “Amazon Music” now “has tens of millions of paid customers;” and its “Amazon Fashion” online retail portal now “has become the destination for tens of millions of customers.”

From Bezos’ shareholder letter:

Congratulations and thank you to the now over 560,000 Amazonians who come to work every day with unrelenting customer obsession, ingenuity, and commitment to operational excellence. And on behalf of Amazonians everywhere, I want to extend a huge thank you to customers. It’s incredibly energizing for us to see your responses to these surveys.

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’. I see that cycle of improvement happening at a faster rate than ever before. It may be because customers have such easy access to more information than ever before – in only a few seconds and with a couple taps on their phones, customers can read reviews, compare prices from multiple retailers, see whether something’s in stock, find out how fast it will ship or be available for pick-up, and more. These examples are from retail, but I sense that the same customer empowerment phenomenon is happening broadly across everything we do at Amazon and most other industries as well. You cannot rest on your laurels in this world. Customers won’t have it.