incrediBILL - 12:02 am on Jan 14, 2011 (gmt 0)
We can't make assumptions without actually knowing what goes on behind closed doors. The only actual, concrete data people have - is what they see in their adsense earnings.
That's not true at all.
You can make assumptions based on observations, and since you can run both AdWords and AdSense it's easy enough to make a very site targeted ad campaign, get someone to click it for you, and compare how much you spent vs. how much you earned.
Many proved years ago it was a 70% split long before Google finally admitted it was a 71% split but nobody wanted to hear that.
I personally saw the amount on a contract for a Premium Publisher, nobody wanted to hear that either.
When the ads go off target, except the image ads, it's more often than not the actual on-page SEO is broken, proved it many times, but nobody wants to hear that either.
I see swings in CTR all the time, and it's always the result of the ads being displayed not matching what my visitors want, it either appeals, or it doesn't. Sometimes blocking a few of them solved the problem and in a couple of rare instances I had to solicit help from Google to fix what turned out to be a bug. However, Google doesn't actually control the CTR, your visitors do. Sometimes the best paying ads are the least interesting ads to your visitors yet Google pushes them hoping to get the bigger payouts.
Nobody said anything about trusting Google, the big corporation, my only point is that people like to just sit back and say "I did nothing new, now it's all in the toilet".
Just because nothing changed on the site doesn't mean something wasn't quite right in the first place which, once Google makes a correction, alters the outcome on your site.
This can be easily evidenced by the evolution of Google's WMT's which keep pointing out issues on sites that "never changed" but now need to change to fall back into line with the compliance validation being performed.
Obviously there have been a few sites that have inexplicably slid to rock bottom, but I'm sure if a little research was done there would be an explanation.
There is usually some kind of clue.
Like I said before, sites that can't adapt to these changes won't survive on the web.