Any statistics available regarding relative popularity of OpenId providers?

Question

I'm using OpenId, and am providing buttons for all the usual suspects, but I'd like to be a little more scientific about it.

Are there any public stats regarding numbers of users for each provider?

Answer 1

Why are you "providing buttons for all the usual suspects" ?!

One of the main reasons for OpenID is to avoid the NASCAR problem (which requires buttons for all the usual suspects).

One OpenID button should be enough.