CDC on Mobile Phone Penetration

They have the most accurate stats. [Link]

In a report released today, the NCHS says that the number of wireless-only households rose from 3.5 percent in 2003 to 17.5 percent in the first half of last year. Actual numbers of those households aren't available, but in 2003, 6 million adults and 2 million kids were wireless only, compared to 36 million adults and 12 million children in the first half of last year. By now, more than 20 percent of households are wireless only, NCHS senior scientist Stephen Blumberg tells ScientificAmerican.com. In two states, Oklahoma and Utah, more than a quarter of households keep only mobile phones.

Why is this an issue? Wireless-only folks differ from those who still keep a landline, Blumberg explains. Not only do they skew younger, but they behave differently, too. Introduce those differences into health surveys, he says, and the results are biased.

Half of wireless-only users are under 30 years of age, but the greatest predictor of whether they rely solely on a cell phone is if they own or rent: renters are four times as likely to be wireless-only as are people who own their homes, Blumberg says. On top of that, they're more likely to live in metropolitan versus rural areas, and in or near poverty.

That said, "even if we control for age, renting, income, education, for family structure, where they live, race — minority individuals are more likely to be wireless only — we still see health differences," Blumberg says. "Wireless-only [users] are more likely to binge drink, they are more likely to smoke, they're more likely to be uninsured so therefore, if these wireless-only adults are excluded from these surveys, they may underestimate binge drinking, smoking and the prevalence of uninsured adults. That's why the CDC is concerned."