Does Google Analytics skew data for web owners with traffic using Windows Phone? Not quite. While there is no clear categorisation between iPhone/iPod, PC and WP7 the data is being collected and it's available for viewing. With the list of operating systems in the filter, one can select screen resolution as a secondary dimension to compare the OS and resolution numbers.
An article, posted back in June, over at Mobility Digest saw them go into some depth with their analytical data while calculating the percentage of visits between the mobile platforms. This article publishes detail for Android, Windows and iOS - note "Windows" and not "Windows Phone". Doug Simmons then took a further look into the numbers as he thought WP should be reporting higher values.
I too was interested so I took a quick look at my personal website (since it doesn't receive a whole lot of traffic it should be easier to break down the data) and filtered through the visits recorded in Google Analytics. The majority of my traffic comes from WPCentral with redirects from Twitter and other locations that involve Microsoft's platform, so I predicted that a healthy portion of the mobile traffic should be using WP handsets.
In the image above you can see the screen resolution and OS filters enabled. It's quite clear that Windows Phone is being picked up by the tracking code, but is merely being categorised as "not set" (one of the resolutions paired with Windows is also 480x800). I'm actually fairly surprised seeing how the platform has been out for almost a year, Google has had ample time to fix this issue of Windows Phone not being recognised as well as Windows Mobile.
MSIE 9 will count for both the mobile and desktop hits and the only way to accurately guess as to how much traffic is on Windows Phone lies with the screen resolution and browser/OS filtering. It's not much but at least we're not being ignored. It's just a massive negative for web owners who would never see Windows Phone while looking at mobile traffic data. We're not that small Google!
Oh, if you use Google Analytics and have just ventured onto WP7, check out Phonealytics.