I went to the Neilson's website once (I forget what it is now) looking for the same thing.
They said they dont disclose ratings like that because they dont want that information to sway anyone's viewing habits.
For example, if you usually watch SHOW A on Monday nights, but find out that SHOW B's ratings are three times higher than the show you usually watch, you might be influenced to watch show SHOW B to see what all the hubbub is about.
This is pretty much my favorite show on the tv right now. The drama was turned way down this week 'cept for Tammy trying to start some shit. I thought all the guys might vote for her, but maybe she's right and they all are big pussies.