Amazon.com Inc. convinced 10 million U.S. consumers to join its Prime membership program from June 2017 to June 2018, with Consumer Intelligence Research Partners (CIRP) estimating the program had 95 million members in the United States as of last month.

CIRP’s membership estimates are based on the results of an online survey of 500 online shoppers. Amazon does not disclose how many Prime members it has by country; however, earlier this year it said it had more than 100 million globally.

The 10 million new U.S. members is a significant slowdown in membership gains. From June 2016 to June 2017, Amazon Prime gained 38 million members, according to CIRP.

“As expected, the rapid growth in membership slowed. Membership grew 12% in the past 12 months, down from 35% growth during the previous 12 months,” says Josh Lowitz, CIRP partner and co-founder. Lowitz says he expects Prime growth in the U.S. to continue to slow.

The majority of U.S. online shoppers are already Prime members, so the market for new members is drying up. CIRP estimates 59% of Amazon customers in the U.S. are Prime members. Taken further to the household level, as many Prime members share their benefits with others in their household, the 95 million membership number means about 75% of U.S. households have access to a Prime membership, per Internet Retailer estimates using Census Bureau figures for U.S. households. (This does not take into account households that may have multiple individual Prime accounts.)

A portion of the 10 million members who signed up over the last 12 months will have signed up on Amazon Prime Day 2017. Amazon says more new Prime members joined during that sales event, held last year on July 10, than on any day in its history. Amazon Prime Day 2018 kicks off this afternoon and runs through July 17. Amazon Prime Day promotions are available only to Prime members. Internet Retailer projects Amazon will generate $2.5 billion in sales in the United States during Prime Day this year, up 60% from $1.56 billion last year.

U.S. Prime members spend an average of $1,400 annually with Amazon. Consumers who are not Prime members spend an average of $600, CIRP says.

Amazon raised the price of a Prime membership in the United States to $119 in May, up from $99. It was the first price increase in Prime since 2014. Prime is available to consumers in 17 countries.