Low CPM, what happened?

Low CPM, but no change with CTR and pageview

[alexandra]

Very low CPM than normal stat in the past two days, but my CTR and pageview are the same as before, anyone can tell me what happened? Actually, my question should be how CPM is calculated?

Thanks
Alexandra

[coho75]

CPM is calculated by:

1000/page impressions * Your earnings = CPM

Lets say that you have 500 page impressions and earn $25 from all clicks.

1000/500 * $25 = $50 CPM

Hope this helps. There are probably a few other ways to figure it.

coho75

[loanuniverse]

Coho is right "that is the way, it is normally calculated"

However, Google takes into account every impression of an ad unit into account on its calculations. You might have two impressions per page view now that more than one ad unit is allowed per page.

It throws a monkey wrench into the whole thing.

anyone can tell me what happened?

If impressions and CTR are the same, then it means that visitors clicked on cheaper ads.