38% of US households use Amazon Prime

Amazon's (NASDAQ:AMZN) Prime membership program continues to grow and now has close to 41 million members—some 38 percent of U.S. households, according to a new survey by Cowen.

Membership jumped 32 percent in December compared the same period in the prior year. Amazon Prime Day helped boost those numbers. In spite of widespread criticism that product offerings were weak, the event drove shoppers to sign up for Prime by the thousands and added 1 percent to Amazon's overall sales.

Prime is a juggernaut for Amazon. The retailer added 3 million new members in a single week leading up to Christmas and Prime members are younger and wealthier, according to an earlier survey by Cowen.

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