These last days I've been having very low cpm. But since yesterday, it raised out of the blue, and I haven't change anything in my page, visits are the same, etc. So why is this change? Just to give a figure (not real values), imagine having $0.3 - $0.5 cpm, and then having $15 cpm. Today is also a high value, but how to make it keep it like that?
The eCPM/CPM with Google Adsense varies alot from day to day. It's not strange seeing it jump so suddenly and fall back again. A few days is definitely not something you should worry about.
But what's the reason for this change? Anybody knows? There have been 20 days aprox. of low cpm, and then this abrupt change. What makes this change so much? And no, I'm not being targetted, or anything. As I mentioned before, impressions are stable, as well as other statistics.
And also, not that I'm worried. I'm getting more money this way.. that's why I'd be interested to keep it high ;-)
Their are so many variables that it's extremely hard to speculate. It depends on the nature of your site, perhaps advertisers are bidding more now that it's the start of a new month. It could be anything.
It's often the case that the keywords you are using are enjoying a life in bid prices. Figure out what your keywords are, then use the Overture bid tool to get an idea. http://uv.bidtool.overture.com/d/USm/search/tools/bidtool/