I’ve been around Adsense, and here long enough to know that fluctuations in clicks, ctr etc can be caused by almost anything, and jumping to conclusions is a pointless excercise.
However, I have made one change to my website that seems to have made a difference to all of the above, and a subsequent rise in income.
Most of my site visitors are in the US, but as I’m located in the UK so was my web hosting. I figured it didn’t really matter where the host was. I have recently moved hosting to the US for a variety of reasons including the fact that most of my visitors are there, and it just might give them a faster load time to the pages. I guess that the pages load faster in the US now - they are certainly loading faster here.
Interestingly enough, the effect was immediate once the domain had transferred. ctr and clicks went up. I’ve always kept the pages minimalist so as to provide faster loading times - especially the main index page. If the assumptions are correct, then it would appear that the load times are pretty crucial to if a visitor stays, and if they click or not!