I recently added a 468 AdSense banner to the top of my pages. I was happy to see a very high click-through rate, which probably isn't a surprise to the veterans on this forum. The clickthrough rate over the past month was more than double the rate of the 160 x 600 on the right side of my pages. But then I noticed that the 468 had a revenue per click that was only half that of the 160 x 600. The lowest click rate with the highest revenue per click was the 300 x 250 that only partly shows above the fold of the browser. Why would the ad with the highest rate generate the lowest revenue per click, while the ad with the lowest rate have the highest revenue per click? One possibility that comes to mind is that more image ads run in the 300 position, but I can't prove that's the case. Any insights?
good job Im still familiarizing myself with google adsense.. hope i can answer your questions in the future
While I understand the logic behind this, in my experience it isn't the case. I recently trimmed the ad units on my page from 3 units and 2 link units to 1 each. The ad payouts were the same. In my case though, the niche is extremely low ppc, so it depends on your niche.