Has anyone else experienced that with Adsense in the last week your earnings have dropped for the same type of adds, impressions and CTR?
RSG this has been discussed already and the consensus is some publishers agree with you and other don't. That's just how it is. I had 20 clicks on a site for $1 yesterday so I am with you.
I think you will find more often than not it generally has to do with the amount of competitive in your industry. If a few big players decide to stop their adword campaigns or drop their prices per click that will reduce competition so the others would follow suit creating generally lower prices. Alternatively if more sites (ad space) enters the industry advertisers don't have to compette as much for exposure because there is more ad space to go around. I think you will find these are the reasons that your CPC has dropped.
It depends on the bid of the advertiser sometimes it happens to me also revenue for 4 clicks is more than revenue of 10 clicks on some other day