• by Mark Walsh  @markfwal, February 21, 2012

U.S. smartphone penetration is nearly at the halfway mark as of January, according to the latest Nielsen data. The 48% of American adults with smartphones is up from 44% in the third quarter of 2011. It likely reflects a bump from the record 37 million iPhones that Apple sold worldwide in the fourth quarter.

Nielsen tends to be the most aggressive among research firms when it comes to estimating how many Americans have smartphones. Most put the level closer to 40%. comScore, for instance, estimated smartphone penetration as of December at 42%. The Nielsen findings are based on a survey of 20,000 mobile users.

Younger adults are more likely to have smartphones. The 24-34 age group had the highest proportion of smartphone owners at two-thirds. That was followed closely by people ages 18-24, at 62%, and people 35-44, at 58%.

Looking just at consumers who bought smartphones in the last three months, the pattern was similar. Eight out of 10 people 18-34 have gotten smartphones in that period, leading all other age segments.

But Nielsen noted income level is also a key factor in how likely someone is to own a smartphone. When both age and income are both taken into account, older subscribers with higher incomes are more likely to have a smartphone. For instance, those in the 55-64 age bracket making over $100,000 a year are almost as likely to have a smartphone as those 35-44, making $35,000 to  $75,000 per year. 

In the same vein, people 45-54 making more than $100,000 a year are almost twice as likely to have a smartphone as those in the same age group making $15,000 to $35,000 a year (60% versus 32%). When combining age and income, those 25-34 making more than $100,000 had the highest proportion of smartphone owners, at 80%. But among people in that age range making only $15,000 to $35,000 a year, more than half (58%) had a smartphone.