signor_john - 4:20 pm on Dec 3, 2008 (gmt 0)

I ended up having an extremely strong Monday and Tuesday in terms of traffic, and EPC was fine. However, CTR was lower than usual, resulting in a noticeably smaller-than-normal eCPM.

Was Google cheating me? Nope. On closer examination, I could see that the jump in traffic was caused by a news event: People were reading about the news event and going to Web search to learn more about the topic, which led them to my pages on that topic. To judge from bounce and exit rates, most of those people found the information they were looking for and moved on. And because they were interested in the event, not in researching purchases, they had no reason to click on AdSense ads.

I expect that traffic, AdSense CTR, and AdSense eCPM will return to their usual November-December levels as soon as interest in the news event has faded.