I do not really know the answer to this, just a question, but I will say this, the more ads you serve on your page, could affect the dollar amount you receive from those clicks. I have done this before and maybe you can do the same and let me know. Decrease the number of Google Adsense Ad Units on your page and see how it affects your overall performance. I actually decreased my number of units and noticed an increase in revenue, there could be several possibilities for this.
My PageRank could have improved because I was serving a lower number of Adsense units and thus making my CTR higher. Or, Google Adsense may have served better paying ads because of the decrease in placement. I guess I am a conspiracy theorists, but it just seems odd to lower your Adsense Units and get higher payouts. But, lets be practical, this could have been because the page was not so cluttered and camouflaged the ads better into the Content, which we all know that Quality Content Is King!
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