One of the topics that the CDC's annual National Health Interview Survey (NHIS) digs into — a sort of check-in on key US health and demographic information — is landline and wireless telephone use in households, and this year's numbers reveal an unsurprising trend: across nearly every category of people, landlines are dying a slow death.

But when you dig into the details, some of the numbers are surprising. For instance, technology is far too often associated with the middle-class and the rich, inaccessible by the poor. With wireless, though, adults living in poverty are more likely to live in a wireless-only home than their more well-off counterparts: 59.4 percent versus 42.5 percent for those making more than twice the poverty line (the threshold for what the NHIS calls "Not Poor"). In that segment of the market, the many, many prepaid carriers and plans available may be filling a need that landlines have not.

Other trends hew more closely to what you might expect. The wireless-only lifestyle is most common in the 25-29 and 30-34 age groups, at 69.2 and 67.4 percent respectively in the most recent reporting period, July to December of 2014. It's slightly lower in the 18-24 demographic — 58 percent — likely because these individuals are more likely to be living at home with their parents, an age group where landlines become far more common. At 65 and over, landline-free households represent just 17.1 percent of the surveyed group.

And the least likely to have a landline? That'd be adults living with other unrelated adults without children — i.e. roommates — where just 18.7 percent have an old-fashioned phone in the house. That makes sense, considering that each roommate is living their own life and has little interest in sharing a single phone. Overall, some 45.4 percent of households are wireless-only, an increase of 4.4 percent against the same period a year prior. And the rate of adoption is accelerating: the year before that, NHIS saw a 2.8 percent change.

American landline operators have been angling to start phasing out copper service for some time, replacing it with more modern (and, in many cases, cheaper-to-maintain) services like fiber and wireless. It may seem like a win-win, but old-school, circuit-switched copper has one thing going for it: bulletproof reliability, which has been a sticking point for migration in light of 911 concerns. And, of course, there's the simple fact that the most rural parts of the US still often lack reliable cellular service. But for many, it seems that those concerns are starting to evaporate on a wide scale.