For our website, Google Analytics reports an excessively high number of Internet Explorer 7 users (40%). As we drilled further into the data, we found that the majority of these IE7 hits were coming from newer operating systems like Windows 7, where IE7 was never a default installed browser. It does not seem plausible that we actually have this many (or any) users visiting our site with IE7 within Windows 7.
Why are our Internet Explorer 7 numbers so inflated as reported by Google Analytics?
This has to do with the user agent reported by the browser when the site has been added in Tools->Compatibility View Settings.
Experimenting with IE11, I found that if I visit a site normally, the user agent string is:
This indicates IE11
If I open my browser's compatibility view settings, and add my domain to the list of those that should render in Compatibility View, this is my UA string:
This indicates IE7
I used this website to give me a cleaner explanation of the data in these UA strings: http://user-agent-string.info/
One interesting thing is that I can still control what mode the page renders in using the x-ua-compatible meta tag. So, if my website makes strong use of x-ua-compatible to force "edge" mode, visitors using IE11 with my domain set to compatibility view will actually render by page in IE11 mode, but will report IE7 to Google Analytics.
For our organization, the reason the IE7 number is inflated is because at one time, it was the practice of our tech support team to advise our users to add our website to their compatibility view settings to avoid issues with our legacy web apps not working in IE8.