The latest version of Microsoft's mobile platform rolled out at the end of October after its predecessor, Windows Phone 7, failed to set the world alight.
However, speaking during at guest appearance during Qualcomm's presentation showing off Nokia's Lumia 920 and HTC's flagship Windows Phone 8X in the process Ballmer claimed the new OS is building evident momentum.
Five's alive
"In November we reported that sales of Windows Phones were four times greater than the same time last year," Ballmer told Qualcomm CEO Dr. Paul Jacobs.
"During the week of Christmas, we were running at five times the number of phones during the Christmas week of last year."
Of course, given Microsoft was always suspiciously quiet about Windows Phone 7's performance at retail, selling at five times the rate though undoubtedly good news arguably doesn't mean all too much.
Graph of growth
The news, nonetheless, comes as an infographic posted by PocketGamer.biz illustrated the growth of the platform's marketplace.
Numbers suggest Windows Phone Store is growing at a faster rate than Google Play at the same stage of its life and isn't tracking all too far behind the App Store.
You can view the infographic in full here.
