Vamm - 8:20 pm on Jun 2, 2010 (gmt 0)
As a side note, when you reference AOL leak data (and I reckon the same also applies to the Chitika data), you should take into account that CTR distribution is different for different length of key phrase.
Also, there is a specific category of searches that contain "www." in them. This is when someone accidentally types a domain name into a search box.
So you get, based on AOL dump
For a query containing "www.", #1 CTR is 70%, #2 is 10%.
For a single word key phrase, #1 CTR is 60%, #2 is 13%.
For a four word key phrase, #1 CTR is 30%, #2 is 13% and #3 is 10%.
There is a visible difference between long tail multiple words queries and short queries. The trend is like "short query = significant difference between #1 and #2, long query = less difference".