Webwork - 8:10 pm on Jan 15, 2011 (gmt 0)
I think the message, implicit in the lack of response, is this: normal tends to be a range, not a "point".
Also, there's likely a dozen reasons for why any site may experience an increased CTR including better targeting, seasonal variables, better ad copy, etc.
Of course, you will now be banned for discussing a topic that is verbotten by G's TOS. :-/ and :P