Windows Phone might make up only a tiny sliver of all smartphones sold in the US, but the country is the biggest market for Microsoft's mobile OS.
US smartphone owners account for 11 percent of all Windows Phone users, making it the largest individual market for the OS globally, according to new figures from ad network AdDuplex.
The figure was based on ads served by AdDuplex through 11 global apps to around 200,000 devices over the course of one day in July.
A country by country breakdown of Windows Phone users across the world casts a different light on the importance of the US to Microsoft's mobile ambitions, and comes against a background of other reports showing Windows Phone's stubbornly low share of the US smartphone market compared to rivals Android and iOS. According to market researchers Kantar Worldpanel, Windows Phone has around four percent of the smartphone market in the country.
Behind the US, India has the next largest Windows Phone population, accounting for 7.5 percent of Microsoft's Windows Phone users, followed by Brazil with 6.9 percent.
Russia and Italy account for 4.3 percent each, while China, Mexico, and the UK stand for 3.7 percent each. Meanwhile, Germany, Argentina, Thailand and Finland represent between 3.5 and three percent of Microsoft's Windows Phone user base.
According to recent figures from Gartner, Windows Phone's share of global smartphone shipments so far this year is around four percent. However, the analyst firm expects the OS to rise to 10 percent by 2018. It doesn't say what factors it expects to drive the change, but Gartner's predictions are notably lower than the 15 percent share Microsoft said it was targeting for 2018 when it announced its acquisition of Nokia's devices and services business last year.
Smartphone OS sales figures last month from Kantar Worldpanel ComTech showed mixed results for Microsoft's mobile fortunes across the world.
Windows Phone's share of OS sales in the US fell to 3.8 percent in the three months to May 2014 — down from 4.7 percent in the same period last year, and from its historical peak of 5.6 percent earlier in 2013.
On the other hand, Windows Phone has climbed to between nine and 10 percent of sales in Great Britain, France, and Italy, bumping up its share of sales across Europe's biggest five economies to 8.1 percent from 7.1 percent a year ago.
Perhaps most concerning for Microsoft's OS and devices is, while China accounts for three percent of Microsoft's Windows Phone users, its sales in the country have slipped from three percent last year to 0.6 percent this year with the country dominated by Android at 82.7 percent, followed by iOS at 14.7 percent.