This may be deliberate to thwart those trying to game the program
I did have those kind of tin foil thoughts initially! For example, whereas we might get 100 clicks on one site per day at around $0.77 a click. We will get 1 click ... at $8.97 earnings for that click. It's just odd.
I too have been experiencing severe CTR depressions since the 11th.
Well, that's what I was hoping to read when I came on forums. i.e. hundreds of people saying their CTR had dropped since the 12th. Then I could hope that Google were going to fix it. But I'm on 3 different webmaster forums and no-one else seems to have raised this issue?