Windows Phone may be the fastest growing OS over the next five years but they will still only ship as many handsets  in 2017 as Apple did in 2012, according to Analysys Mason.

The analyst’s recently published report, Smartphone Markets: Worldwide Trends, Forecasts and Strategies 2012–2017, predicts that shipments of Windows Phones will grow from 11m units in 2011 to 136m in 2017. This, however, will still only give the OS a 9% share of the world’s smartphone shipments, compared to Apple’s 23% and Android’s 58%.

The report the report also predicts that smartphone upgrades will drive three out of four smartphone purchases by 2017, up from less than half today.