A new research report from IDC says that wearables powered by the Android Wear operating system will be more than twice as prevalent in the wild by 2019 than they are today.

IDC said that while Android wearables account for only about 17 percent of the market in 2015, they’ll account for more than 38 percent of the worldwide market by 2019.

The Apple Watch and the watchOS operating system will remain dominant in the wearables market for the rest of the decade, but will lose market share year by year. WatchOS devices account for almost six out of ten wearable devices on the street this year, but will account for less than half in 2019.

Top Five Smart Wristwear Operating Systems Shipments, Market Share, and 5-Year Growth Rate (Units in Millions)

Smart Wristwear OS

2015 Shipments

2015 Market Share

2019 Shipments

2019 Market Share

2015-2019 CAGR

watchOS

13.9

58.3%

40.3

47.4%

30.6%

Android/Android Wear

4.1

17.4%

32.6

38.4%

67.5%

Pebble OS

2.1

8.7%

2.6

3.1%

6.4%

RTOS

2.0

8.3%

7.6

9.0%

40.1%

Tizen

1.6

6.7%

1.8

2.2%

3.7%

Other

0.1

0.6%

0.0

0.0%

-100.0%

Total

23.8

1.0

85.1

1.0

37.5%

“WatchOS, in its first year on the market, will quickly establish itself as the overall leader in the smart wristwear market and maintain its position throughout our forecast,” IDC said in a statement. “[The Apple Watch] will, however, see its market share erode as other platforms — particularly Android Wear — gain greater salience in the market.”

IDC said Android wearables will see “market-beating growth” as more and more brands release their own Android Wear wearables in more styles and price points.

The report said total wearable device shipments will reach 76.1 million units in 2015, up 163.6 percent from the 28.9 million units shipped in 2014.

By 2019, worldwide shipments will reach 173.4 million units, resulting in a five-year compound annual growth rate (CAGR) of 22.9 percent. The numbers include both simple wearables, like fitness trackers, and more complicated smartwatches, IDC pointed out.