Americans are increasingly hopping on the smartwatch bandwagon, according to new data from The NPD Group.

Sixteen percent of US adults—or about one in six—now own a smartwatch, up from 12 percent in December 2017, the market research firm said Tuesday.

During the 12-month period ending in November 2018, smartwatch makers raked in nearly $5 billion in sales, up 51 percent from the same timeframe a year earlier. Smartwatch unit sales, meanwhile, jumped 61 percent during the period.

That growth was primarily driven by consumers aged 18 to 34, NPD said; 23 percent of people in that age bracket own a smartwatch.

"Over the last 18 months smartwatch sales gained strong momentum, proving the naysayers, who didn't think the category could achieve mainstream acceptance, had potentially judged too soon," Industry Analyst and Director for NPD's Connected Intelligence practice Weston Henderek said in a statement.

The introduction of smartwatches with built-in LTE—such as the Apple Watch Series 3 and 4, Samsung Galaxy Watch, and Garmin's new Vivoactive 3 Music—"proved to be a tipping point," he added.

"Consumers… now recognize the value in being able to complete a wide range of tasks on the device including receiving notifications, messaging, accessing smart home controls, and more," Henderek said.

Going forward, NPD expects "a big boost in penetration among older segments" as health-focused smartwatches such as the Apple Watch Series 4, which features fall detection and ECG capabilities, continue to gain popularity. Apple's latest smartwatch earned an "excellent" rating in PCMag's review and our coveted Editors' Choice award.