I just recently noticed that my CTR is down almost 5 times , the traffic has although doubled . Also the revenues are sucking up .
There definitely seems to be some weird things going-on with Google. My PR has crashed, but the total number of visitors I have is up. The CTR has decreased slightly but me AdSense earnings remain stable. Some of this is probably because I've diversified out of Google to get traffic.
when his traffic doubles and CTR drops down 5 times (i think what OP meant is 1/5th), then it cannot be due to smart pricing. smart pricing only applies when there is a click and is being paid accordingly. if traffic doubles, then CTR should double also. you might wanna try different ad placement.