Cowen analyst John Blackledge estimates that Amazon.com (NASDAQ: AMZN) exited 2017 with a record 60 million U.S. Amazon Prime subscribers, the third year in a row of 10 million U.S. sub additions.

"In December '17, ~54% of respondents indicated that they lived in a Prime household, which we estimate corresponds to ~60MM US Prime Households, up ~10MM from ~50MM USHHs in Dec '16." Blackledge commented. "Our survey suggests that overall US Prime households in Dec '17 were +19% y/ y, an acceleration versus the +13% y/y growth in Nov '17. Moreover, Prime added ~10MM incremental US Prime Members in '17 for the 3rd consecutive year, per our Survey, despite a much larger base each year."

In their view, Prime remains the most critical driver of Amazon's eCommerce business long-term.

The firm maintained an Outperform rating and price target of $1,500 on AMZN.

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Shares of Amazon.com closed at $1189.01 yesterday.