There were about 197 million people in the U.S. using Prime as of March, including some who aren’t paying for it, according to estimates from Consumer Intelligence Research Partners. Other estimates suggest there are between 140 million and 160 million U.S. Prime members. Amazon hasn’t provided a figure.
Josh Lowitz, a partner at CIRP, said his firm calculates the number of users who enjoy Prime free shipping but aren’t in the member household to be somewhere in the “low tens of millions.”

When user growth stalls, don’t allow the sharing of passwords. Netflix did it, now Amazon is running their version.