Amazon Prime boxJohn Blackledge, a Cowen and Company analyst, estimates half of the households in the U.S. could have Amazon Prime by the end of the year — unless they already do.

In a report shared with CNBC, Blackledge estimates there are 49 million existing Amazon Prime members, comprising 44 percent of homes nationwide. He predicts about 12 million new subscribers will sign up in 2016, bringing U.S. households represented to just over 50 percent.

But Amazon may have already passed that benchmark. In July, a study by Consumer Intelligence Research Partners (CIRP) estimated Amazon’s Prime program had reached 63 million members in the U.S.

cirp

Analysts can only speculate about the number of Prime subscribers nationwide. Amazon is tight-lipped when it comes to that data. But we do know one thing for certain: The e-commerce giant is adding subscribers to its $99 per month membership program at a breakneck pace.

Amazon added 10 million new Prime members last year and seven million in 2014, according to Blackledge via CNBC.

Amazon has been steadily rolling out new features that add value to its Prime program. Free two-day shipping has always been Prime’s bread and butter, but now members also get access to vast video and music libraries, audio programming, and Prime Now same-day shipping. Amazon is also courting non-committal customers with a $10.99 monthly subscription.

Prime’s rapid growth is good news for Amazon. Prime members spend more on average, about $1,100 per year compared to the $600 per year for non-members, according to CIRP. They also tend to be more loyal, and Amazon retains about 95 percent of them after one year.

“We are very happy with the growth,” Amazon CFO Brian Olsavsky said in January, when Prime memberships grew faster than analysts expected. “We just continue to make the program as valuable as we can.”

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