As the juggernaut rolls on, Amazon Prime surpassed 100 million members in the U.S. in the fourth quarter, according to new data from Consumer Intelligence Research Partners (CIRP), representing 62% of all Amazon customers.

Just six months ago there were 85 million Amazon Prime members in the U.S., according to CIRP, an indication of the continuing growth and penetration of the sticky subscription program. Prime members are a bounty for Amazon, spending on average $1,400 per year vs. $600 for non-members.

“Membership growth has slowed, but continued steadily in the holiday quarter,” said Josh Lowitz, Partner and Co-Founder of CIRP. “U.S. membership grew 10% in the past year, slower…