| Microsoft | Dec-10 | Jan-11 | Feb-11 | Mar-11 | Apr-11 | May-11 | June-11 | July-11 | Aug-11 | Sept-11 | Oct-11 | Nov-11 |
| US installed base | 8.4 | 8 | 7.7 | 7.5 | 6.7 | 5.8 | 5.8 | 5.7 | 5.7 | 5.6 | 5.4 | 5.2 |
| Percent loss | 0.6 | 0.4 | 0.3 | 0.2 | 0.8 | 0.9 | 0 | 0.1 | 0 | 0.1 | 0.2 | 0.2 |
Comscore has released their latest US market share numbers, and while it shows the US market grew to 91.6 million smartphone users, the number of users running a Microsoft mobile OS has dropped, not just in market share, but also absolute numbers.
Now only 4.75 million users run Windows Mobile or Windows Phone, down from 4.89 million in September. That is 14,000 less users that September, and likely shows the influence of the launch of the iPhone 4S.
With the low US Windows Phone market share the Comscore numbers will likely continue to fall for some time before we see a turn around.
See the full report here.