It seems that the iPhone 6 is the most widely distributed single model of Apple’s phones, with the 5S and 6P having roughly equivalent penetration.
There were some Wall Street analysts who feared that the Phone base seems to be slowing down, and it appears these fears have been confirmed. Growth of the iPhone base looks to have slowed in the recent past. According to the CIRP, the average sequential growth for the past two years has been nine percent per quarter. They also said that “the US installed base of iPhone users roughly doubled from December 2013 to December 2015.”
The data that CIRP uses is a combination of both sales data and consumer surveys to arrive at their current numbers.
Based on the CIRP iPhone owner estimates and comScore’s market share figures, that means that the US smartphone market is made up of roughly 260 million people.