While only 43% of all US mobile phone subscribers own a smartphone, the vast majority of those under the age of 44 now have smartphones, according to Nielsen's third quarter survey of mobile users. In fact, 62% of mobile adults aged 25-34 report owning smartphones. And among those 18-24 and 35-44 years old the smartphone penetration rate is near 54%.

Other groups show slightly lower penetration rates. Around 40% of 12-17 year-old teens and 40% of 45-54 year-olds reported owning a smartphone, as opposed to a more basic feature phone. After younger adults, the segment with the second fastest-growing smartphone penetration rate is those aged 55-64. Smartphone penetration among this older group is only 30%, but it jumped 5% this quarter.

As the smartphone market continues to expand, Android remains the most popular smartphone operating system in the US, with 43% of the market, while Apple is the top smartphone manufacturer, with 28 percent of smartphone consumers sporting an Apple iPhone.