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Amazon Prime members spent nearly double the amount spent by non-membersGetty Images

Amazon Prime's membership rose 35% during the year 2015, as customers signed in for speedy delivery, especially during Black Friday deals, according to a report by Consumer Intelligence Research Partners. The number of Prime members in the US reached 54 million, or about 47% of all customers.

The report found that US customers spent on average about $1,100 per year while non-members spent about $600 per year. Josh Lowitz, partner and co-founder of CIRP said, "Amazon added 14 million new members in all of 2015."

Amazon Prime is a paid member service introduced in late 2011. It includes free two-day shipping, unlimited and ad-free songs, unlimited photo storage in Amazon Cloud Drive, free books and more.

While growth was spread evenly across the year, a majority of the sales were seen during the last few quarters, coinciding with Amazon Prime Day on July 15 and Black Friday sale in November. During Black Friday, Amazon opened special offers for Prime members including one-hour delivery and exclusive sale preview.

CIRP is a securities research and market strategy firm. For this report, it surveyed 500 US users who shopped at Amazon.com during October-December 2015.