Anyone have stats on numbers of Google users searching while logged in?

[Gyi]

In light of Google's recent "social search update", I am curious to know how many Google users perform searches while logged into their Google account thereby showing "social results".

[Goetzman]

I'm finding very conflicting results with my clients thinking that they are ranked higher or in some cases lower than what a non-related fresh computer network shows. The social results really are changing the landscape of seo!