Amazon has added almost 20 million new Prime subscribers since last year's Prime Day

Tuesday marks the second annual Amazon Prime Day, when all Amazon Prime members can get exclusive discounts on more than 100,000 products through the company.

This year, more than 63 million people will be able to take advantage of those deals, according to data from Consumer Intelligence Research Partners charted here by Statista. That's up by more than 20 million - or almost 50% - from a year ago. Prime is important for Amazon not only for the $99/year subscription fee, but because members spend more than 2x as much on Amazon every year as non-Prime members.

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