Amazon Prime growth slows

amazon shipping boxes on a desk

There are some 65 million Amazon Prime members in the United States, an increase of 38 percent in just one year, according to a new report.

Data from Consumer Intelligence Research Partners shows that Prime members spend an average of $1,200 a year, compared to about $600 per year for nonmembers. 

RELATED: Amazon opens pop-ups

Amazon does not release Prime membership numbers, but CIRP derived estimates based on surveys of 500 U.S. subjects who made a purchase at in the period from July-September 2016.

The growth rate is slowing somewhat, according to Josh Lowitz, CIRP partner and co-founder. "As Amazon starts to reach a limit of available U.S. households, it saw its annual growth rate decline a bit. Sequential growth, from the June 2016 quarter, also slowed, to 3 percent, compared to 7 percent in the June 2015 to September 2015 quarter, which benefitted greatly from the inaugural Amazon Prime Day."

RELATED: Amazon Prime draws younger, wealthier shoppers

Growth and customer retention are being aided by Amazon's monthly payment plan of $10.99 per month compared to $99 per year, noted Mike Levin, CIRP partner and co-founder. Some 19 percent of Prime members are paying monthly instead of annually. 

“A monthly payment plan is pretty clever, and will no doubt help with conversion rates," Levin said. "Amazon has seen a leveling in the rate at which free trial customers convert to full members, from 66 percent two years ago to 62 percent in the most recent 12-month period."

RELATED: Amazon adds Prime perk, bans incentivized reviews

Amazon continues to add Prime benefits and is expected to offer promotional deals on all programs and Amazon-branded products throughout the holiday season.