Adults age 25-34 have the highest level of smartphone ownership in the US: 62% owned a smartphone as of the third quarter of 2011, compared with 43% among mobile phone subscribers of all ages, according to data from Nielsen.

Adults age 25- 34 are clearly the sweet spot of smartphone adoption, but other generations have surpassed the 50-percent tipping point as well: 54% of adults age 18-24 and 53% of those age 35-44 own a smartphone, as opposed to a basic feature phone.

Other groups show slightly lower penetration rates: 38% of those age 13-17 and 39% of adults age 45-54 own a smartphone.

After younger adults, the segment with the second fastest-growing smartphone penetration rate is those age 55-64. Smartphone penetration among this older group is only 30%, but it jumped 5% in the third quarter.

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Amid the rapid market expansion, Android remains the most popular smartphone OS (operating system) in the US with 43% of the market, followed by Apple with 28% and RIM BlackBerry with 18%:

About the data: Findings are from Nielsen’s third quarter survey of mobile users in the US.