1script - 4:34 am on Jan 31, 2013 (gmt 0)
@Sgt_Kickaxe: Sarge, we cross paths on the matter of images once again, in another thread :) I am looking at the stats of a site that has no images whatsoever, none! Other than template of course. It's about very dry, specialized and unappealing accounting matters. If images would have existed, they would be images of text documents, so they don't - no need. Still showing the same impressions bell curve (left part of it so far, sigh...) with Web or with All filters enabled, so images did not play a role.
Nevertheless, thank you for the idea to look at the filters! I have noticed that in the "Location" filters a sector called "Russia" appeared. Since the site has nothing at all to do with Russia and never had any Russian traffic before, I though it's peculiar and looked at only filtered Russian traffic - impressions start from zero on the 16th, hover just above zero until the 25th and zoom all the way up to the unaccounted 50% of the total traffic on the 27th - an astounding 100,000% increase in Russian impressions in two days. Yandex must have crushed over the weekend and I didn't hear about it (no, seriously, did it?) . I have no content in Russian and the subject matter is very narrowly US-oriented, so, not surprisingly, all these thousands of impressions generated less than 10 clicks (in fact, I think it's just zero).
Anyway, this gets me closer to some kind of an explanation but does only explain one site. I have other sites showing the same impressions explosion and yet they are not as narrowly geographically focused and have had some valid traffic from Russia before. You would think that 100,000% increase in impressions would give me at least some sort of an increase in clicks, and yet it does not.
I am thinking this is probably a reporting error (or feature - however you look at it) which made an entire country (and perhaps several), impressions from which were hidden before and suddenly they started to get counted in total impressions. You would think with big changes like this an announcement from Google would follow...
I am off to checking for signs of other geographically misplaced impressions that may be skewing the stats on my other sites.