As of December 2014, nearly 75% of all U.S. mobile subscribers aged 13 and older owned a smartphone. The highest adoption rates belong to mobile subscribers aged 25-34 (88.9%), and 18-24 (88.6%). In January 2013, the smartphone adoption rates for these groups were 73.5% and 72.2%, respectively.
Interestingly, the two age groups driving much of the growth in smartphone penetration are the oldest and youngest. As of December 2014, 83.7% of teens (13-17) owned a smartphone, up from 58.9% in January 2013. During that same timeframe, the percentage of 55-64-year-olds with a smartphone grew from 40.4% to 61.5%.