Market intelligence firm IDC is forecasting that annual Apple Watch sales will increase from an estimated 13M units this year to 45.2M units in 2019, representing a compound annual growth rate of 36.5%.

The firm predicts that although Android Wear smartwatches will experience even stronger growth of 80.5%, Apple’s much stronger starting point will see it remain the market leader throughout the four year period. By 2019, IDC says, Apple will have a 51.1% market share, with Android Wear next at 38.8% and smaller platforms making up the difference.

The Apple Watch is described as “the measuring stick against which other smartwatches and platforms are compared,” and is said to have two key advantages over other platforms …

Apple’s watchOS will lead the smartwatch market throughout our forecast, with a loyal fanbase of Apple product owners and a rapidly growing application selection, including both native apps and Watch-designed apps.

The growth of Android Wear will be fueled by a mix of technology companies and traditional watchmakers, while it predicts that Pebble will maintain modest growth due to its simple user-interface and low price.

With Apple declining to disclose sales, we’re currently dependent on analyst estimates and channel shipment reports to give some clue as to likely numbers. These estimates are, to say the least, variable. Creative Strategies’ Ben Bajarin recently told a conference that sales will hit a staggering 100M by 2017 – more than double IDC’s forecast for two years later – while Asymco’s Horace Dediu suggested 21M in the first 12 months.

Apple does, however, appear to be pushing hard for growth, with a number of significant price promotions available recently at levels which suggest discounted supply from Apple.