SAN FRANCISCO (Reuters) -Amazon doubled its Prime Day discount sales to four days this year and touted blowout numbers days after the event. But by one critical metric, it missed the mark.

Sign-ups in the U.S. failed to meet last year's total and even the company's own target, according to internal company data reviewed by Reuters.

The world's largest online retailer registered 5.4 million U.S. sign-ups over the 21-day run-up to Prime Day and its four-day sales event from July 8 to July 11. That was around 116,000 fewer than for the same period a year earlier and 106,000 below the company's own goal, a roughly 2% decline in both metrics.

The data, which is not publicly available, offers a rare glimpse into Amazon's vaunted - and closely guarded - Prime business, a paid subscription service that offers fast delivery at no added cost and access to streaming content, among other benefits. Amazon seldom discusses details of its Prime program.

Reuters was unable to determine how many days Amazon used in its calculation for the full 2024 period.

Amazon said it had achieved record-breaking sign-ups in the 25 days around Prime Day, without providing specifics. "Prime membership continues to show strong growth and customer engagement in the U.S. and internationally," the company said in a statement to Reuters.

Prime Day is viewed as the marquee event outside of the holiday shopping season to attract new members to Amazon Prime, two people familiar with the matter said. But subscriptions typically fall off after the event once the discounts disappear, said the sources, who declined to be identified as they are not authorized to discuss internal business.

A pioneer of speedy delivery, Amazon is facing growing competition from Walmart, which has ramped up its own membership program offering fast delivery and other perks.

With the Trump administration's tariffs biting into importers and consumers alike, Wall Street had expected a duller Prime Day than usual, with fewer sellers and discounts.

However, CEO Andy Jassy in a call with analysts in July described Prime Day as Amazon's "biggest ever", citing record sales, items sold, and sign-ups in the lead-up to the event, saying customers saved "billions of dollars."

STRATEGICALLY IMPORTANT

During the four-day event, Amazon signed up 1.6 million Prime U.S. subscribers, exceeding an internal target by about 6%, or 87,000, the data showed.

But in the three weeks prior to Prime Day, a closely-watched internal metric, Amazon registered 3.9 million new U.S. Prime members, 185,000 fewer than during the same period in 2024 and 193,000 below its goal, about a 5% miss in each case.

Reuters was unable to review worldwide data and Amazon declined to make it available.

"Prime is strategically very important to Amazon," said Colin Sebastian, an R.W. Baird analyst. "People on Prime spend more on Amazon and they are less likely to be enticed by competitors' offers of lower prices."  

Encouraged by no-cost shipping, sometimes as fast as one hour, customers tend to buy more from Amazon.com, from e-books to streaming movies and music. Prime members in the U.S., its largest single market, spent an average $1,170 with Amazon in 2024 compared with $570 for non-members, according to Consumer Intelligence Research Partners.

Amazon founder Jeff Bezos once said he wanted to make Prime so compelling that consumers will feel they are "being irresponsible" if they are not members.

Amazon introduced Prime in 2005 for $79 per year and has steadily increased subscription fees, most recently to $139 in 2022. The program drove $23.9 billion in subscription revenue in the first half of this year, making it a key growth driver for the company.

To expand memberships, Amazon has widened its discounted student program to individuals aged 18-24 and offered a six-month free trial. The company also plans to invest over $4 billion to grow its rural delivery network in the U.S.