In the past year the U.S. crossed a mobile tipping point: now, most cell phones in use here are smartphones. According to a new Pew report 56% of all American adults are now smartphone users.

But, as author William Gibson observed: "The future is here; it's just not evenly distributed yet." Here's what Pew had to say about who is least likely to be using a smartphone in the U.S. -- something that could influence mobile strategy for efforts to engage underserved or marginalized communities.

Nearly one in ten American adults still don't use any kind of cell phone at all. Seniors are especially unlikely to own a smartphone: only 18% of people over age 65 currently own a smartphone, compared to 39% of those aged 55-64. This varies significantly by income: only 8% of seniors living with an annual household income under $30,000 own a smartphone, compared to 43% for seniors with an annual income over $75,000.

Whites (53%) are less likely than non-Hispanic blacks (64%) or Hispanics (60%) to own a smartphone.

Low income and low educational attainment correlate with low smartphone ownership: only 36% of American adults with less than a high school education own a smartphone, and 43% of those with household annual income under $30,000. Also, only 40% of rural dwellers own a smartphone, compare to nearly 60% for both urban and suburban dwellers.

The iPhone appears to be an elite device -- probably because there tend to be far more lower-cost Android devices. According to Pew: "Cell phone owners from a wide range of educational and household income groupings have similar levels of Android adoption, but those from the upper end of the income and education spectrum are much more likely than those with lower income and educational levels to say they own an iPhone. Indeed, fully half (49%) of cell owners with a household income of $150,000 or more say their phone is an iPhone. And African-American cell owners are more likely than whites or Latinos to say that their phone is an Android device as opposed to an iPhone."

In fact, Pew found that among smartphone-using adults aged 18-24 (the age range with the highest overall rate of smartphone ownership), only 31% own an iPhone; while 43% own an Android device. Similarly, among non-Hispanic blacks (the race demographic with the highest rate of smartphone ownership), a mere 16% own iPhones; 42% own Android phones. Therefore, mobile strategies to engage these demographics should probably prioritize Android apps over iPhone apps.

It's important to remember that just because someone owns a smartphone doesn't mean they use (or know how to use) its advanced features. Text messaging and taking photos -- both activities that simple feature phones can handle -- are also the most popular mobile activities for smartphone users (over 80% for both). According to a November 2012 Pew report, only 43% of cell phone owners download apps, 50% access mobile e-mail, and 56% use the web browser on their phone.