Another month, another comScore report.

Like the previous reports that have come out, this one seems to back up the notion that Microsoft has yet to stop their losses in U.S. marketshare for their mobile OSs (comScore seems to lump Windows Mobile and Windows Phone). Gathered from more than 30,000 mobile subscribers via an online survey, the data seems to be at least consistent.

Looking at April, Microsoft's U.S. marketshare is down to 6.7%. To put that in perspective, we've accumulated the last few months of data from comScore and we can see that just over a year ago, MS had 13.2% of the market and it had steadily declined to 10.2% in August and 8.4% in December. In short, Microsoft's marketshare has dropped 25% since Windows Phone 7's launch in October.

Of course with the aging Windows Mobile, we expect many to abandon the platform for alternatives like Android or...well Android (and looking closely, RIM gained as well over 2010-2011). But the problem Microsoft seems to have is converting old Windows Mobile users to Windows Phone. Then again, some of those high-end users may be attracted to Android's more "open" standards and OS manipulation, which resembles Windows Mobile in many ways. The decline though seems to be slowing a bit, but until that number becomes positive growth, Microsoft still has much area to recover.

Luckily that Nokia, Skype and Mango strategy should pay off by late 2011.

Source: comScore; via WinRumors