In a report released Thursday, the International Data Corporation (IDC) estimates that Apple sold 3.9 million Apple Watches during the third quarter of 2015 (Q3) for a share of 18.6 percent of the worldwide wearables market. This is a slight increase over the 3.6 million devices the IDC estimated Apple sold during the second quarter of 2015 for what was then a 20 percent share of the market.

This makes the Apple Watch the second most popular wearable device behind Fitbit Inc.’s fitness trackers for the second quarter running. The IDC estimates Fitbit shipped 4.7 million fitness trackers, earning it 22.2 percent of the market.

Home advantage: Chinese vendors capitalize on demand for wearables

According to the IDC, both Apple and Fitbit lost market share to Xiaomi Inc. and other Chinese vendors. Xiaomi maintained its third spot, shipping an estimated 3.7 million wearables in Q3 for a 17.4 percent of the market – an 815.4 percent increase in shipments year-over-year.

Garmin Ltd. increased its shipments by an estimated 400,000 units over the year-ago quarter to claim fourth place while new entrant XTC, a subsidiary of BBK Worldwide – with just one product, the Y01, a children’s phone watch – shipped 700,000 units to beat Samsung Electronics Co. Ltd to fifth place by around 100,000 units.

In total, the IDC estimates that 21 million wearable devices were shipped in Q3, a staggering 197.6 percent increase from the 7.1 million units shipped during the same quarter in 2014.

According to the Ramon Llamas, Research Manager for IDC’s Wearables team, China is the fastest growing wearables market and this has led to Chinese vendors capitalizing on the market momentum at home to seize market share from more established vendors.

36M Apple Watches sold in first year seem unlikely

The IDC report attributes the increase in Apple Watch sales from the previous quarter to Apple entering additional markets and expanding to additional sales channels such as Best Buy. In addition to this, Apple released watchOS 2, enabling native third-party apps for the Watch.

Given the IDC’s estimate that Apple sold 3.6 million units during its first quarter and 3.9 million during its second quarter on the market, it seems unlikely that the Apple Watch will hit the 36 million units some analysts forecast. Given these estimates, Apple is more likely to sell around 12 to 15 million Apple Watches during its first year, a number that’s more in line with Strategy Analytics’ forecast of 15 million.

Image via Fitbit Inc.