april 2014 –
in a historical first, the number of mobile phones in the united states surpassed the numbered population of human beings
wikipedia: list of countries by cell phones in use
this 2015 pew research report does a pretty good job assigning demographics, usage statistics, and consumer sentiment.
not a quick read, the report includes stats, charts, and referenced material.
what the report glaringly misses, are things like financial impact of initial hardware costs, hidden costs associated with upgrades overtime, and any stated reasons consumers felt it necessary to upgrade.