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Last year, Amazon disclosed for the first time the number of Prime subscribers worldwide — 100 million. A new survey estimates that the fast-growing program has exceeded that milestone in the U.S. alone.

In its latest survey, Consumer Intelligence Research Partners estimated Amazon’s U.S. Prime membership at 101 million, and that 62 percent of U.S. households are Prime members. CIRP’s findings are an estimate based on surveys of 500 U.S. subjects who bought something on Amazon between October and December.

“Amazon grew to over 100 million U.S. Prime members in the quarter,” said Josh Lowitz, CIRP co-founder. “Membership growth has slowed, but continued steadily in the holiday quarter. U.S. membership grew 10 percent in the past year, slower than before, but still significant on a huge base and after years of rapid growth. Membership doubled in three years, and almost quadrupled in five years, from 26 million members in December 2013.”

CIRP estimates that 58 percent of Prime members pay the $119 annual fee, versus 36 percent who pay for month-to-month membership and the remainder who are on a free trial. CIRP finds that Prime shoppers spend more than twice as much on an annual basis versus non-Prime customers — $1,400 versus $600 annually.

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