Windows Phone 24.3% Compound Annual Growth up to 2019?

IDC has some new research that roughly correlates with GfK in that smartphone shipments are expected to grow 11.3% in 2015.

IDC2019smartphonepredictions

IDC has predictions up to 2019 when it expects both iOS and Android to grow less, with iOS having the lesser year on year growth. They also predict, without substantiation, that Windows Phone will see a 24.3% compound annual growth.