While the Apple Watch remains the world's best selling smartwatch, the latest data from market research firm IDC reveals basic wearables "reign supreme" as consumers gravitate towards simple, dedicated fitness devices—which also typically cost less than the Apple Watch and other smartwatches.

Shipments in millions (Source: IDC)

Basic wearables accounted for 85% of the market and experienced double-digit growth in the third quarter, according to IDC. Fitbit remained the leader with 23% market share, up from 21.4% a year ago, on the strength of its new Charge 2 fitness tracker. Fitbit shipped an estimated 5.3 million wearables in the quarter.

Xiaomi trailed in second as its $14.99 Mi Band is priced well below any competing wearables, allowing the Chinese company to capture 16.5% market share based on an estimated 3.8 million shipments in the quarter. Xiaomi's market share remained virtually unchanged from 16.4% a year ago.

Meanwhile, the Apple Watch captured just a 4.9% share of the broader wearables market in the quarter based on an estimated 1.1 million shipments, according to IDC. Comparatively, in the year-ago quarter, Apple had an estimated 3.9 million Apple Watch shipments for a much higher 17.5% market share.

"It's still early days, but we're already seeing a notable shift in the market," said Jitesh Ubrani senior research analyst for IDC Mobile Device Trackers. "Where smartwatches were once expected to take the lead, basic wearables now reign supreme. Simplicity is a driving factor and this is well reflected in the top vendor list as four out of five offer a simple, dedicated fitness device. Meanwhile, from a design perspective, many devices are focusing on fashion first while allowing the technology to blend in with the background."

IDC attributed Apple's decline in the third quarter to an "aging lineup" and an "unintuitive user interface." Apple addressed those concerns with Apple Watch Series 2, but the second-generation models launched in mid-September and therefore did not have a full impact on the third quarter.

Apple does not officially disclose Apple Watch sales, instead grouping the device under its "Other Products" category in earnings results.