Sales of wearable devices, such as smartwatches and fitness trackers, are set to increase by 16.7%, from 265.8-million units in 2016 to 310.4-million in 2017, according to predictions from US-based research and advisory company Gartner.

This increase is also set to generate revenue of $30.5-billion in 2017, $9.3-billion of which will be for smartwatches.

This year, Garter points out that up to 41.5-million smartwatch units will be sold.

Besides Bluetooth headsets, smartwatches are on course to account for the greatest unit sales of all wearable devices from 2019 to 2021. By 2021, sales of smartwatches are estimated to total about 81-million units, representing 16% of total wearable device sales.

Gartner research director Angela McIntyre notes that smartwatches are on course to generate the greatest revenue among all wearable devices, reaching $17.4-billion.

She adds that revenue from smartwatches is bolstered by the “relatively stable” average selling price (ASP) of the Apple Watch. “The . . . ASP of the smartwatch category will drop from $223.25 in 2017 to $214.99 in 2021 as higher volumes lead to slight reductions in manufacturing and component costs, but strong brands, such as Apple and Fossil, will continue to be price consistent with the price bands of traditional watches.”

Further, the smartwatches market is currently divided between four types of technology providers, with Apple continuing to have the greatest market share of smartwatches.

However, as more providers enter the market, Apple’s market share will decrease from about a third in 2016 to a quarter in 2021. The announcement of a new Apple Watch expected this month might allow for direct cellular connectivity for interacting with digital intelligent assistant Siri, texting and transferring sensor data when the phone or WiFi is not present.

“We expect other consumer electronics brands, such as Asus, Huawei, LG, Samsung and Sony, to sell only 15% of smartwatches in 2021 because their brands do not have as strong an appeal as lifestyle brands for personal technologies,” says McIntyre.

Two subcategories that Gartner expects to perform well are children’s smartwatches and traditional watch brands, which will emerge as significant segments for smartwatches. Gartner expects children’s smartwatches to represent 30% of total smartwatch unit shipments in 2021. These devices are targeted at children in the 2- to 13-year-old range, after which parents usually provide them with a smartphone.

Meanwhile, fashion and traditional watch brands will account for 25% of smartwatch units by 2021. “Luxury and fashion watch brands will offer smartwatches . . . to attract younger customers,” she says.

Another subcategory is represented by start-up and other smaller, label brands, which will account for 5% of smartwatch unit sales in 2021.

Representing almost half of the market share for all forms of wearable devices, Bluetooth headsets are set to account for 48% of all wearable devices in 2017, with an estimated 15- million devices set to be sold in the year.