You need to see this article that Phandroid has posted (see source link below) that will show you what Google knows about you, how this information is collected, where you can find this information and how you can opt out. Google collects this information, as a form of profiling, in order to better improve their products and services.
You may have already opted out of this collection of information; but, my guess is, you did not.
Did you know that Google knows almost everything that you do on their services? Find out what they know and how you can do something about it.