Hello

I know I wrote an article about “Did you take the display order of your
AdSense ADs into account?” in which I said that it is a known fact that

However reviewing my AdSense statistics today after replacing my
Large Rectangles in my content with medium rectangles I am not
that sure anymore. Or at least the theses needs an additional comment.

I still think that the highest paying Ads are served in the first Ad Unit that
appears in your HTML. However this does not necessarily mean that the
highest paying Ads are shown in the first Ad Unit. I think this effect depends

First some statistics:

My first AdSense Ad Unit (visible and in HTML) on my forum is a
Large Rectangle serving image and text Ads.

My second AdSense Ad Unit (visible and in HTML) on my forum is a
Medium Rectangle serving image and text Ads (switched from a
Large Rectangle a few days ago).

Now comparing the combined stats of those two Ad Units
(to list them on the detailed level I track them would be to much work )
the CTR of my medium rectangle (which is the second Ad Unit) is 118% higher
then the CTR for my large rectangle (which is the first Ad Unit).
The eCPM of my medium rectangle is 165% higher then the eCPM for my large rectangle.
The average CPC is 138% higher for my medium rectangle then the CPC for my
large rectangle.

But how can that be if my medium rectangle is the second Ad Unit on
my page and the highest paying Ads are served in the first Ad Unit?

Let me explain my theory:

for his campaigns. Most of them will use Ad sizes that are industry standard which are:

• 300 x 250 - (Medium Rectangle)
• 180 x 150 - (Rectangle)
• 160 x 600 - (Wide Skyscraper)
• 728 x 90 - (Leaderboard)

Text Ads are independent from the size of the Ad Unit they are displayed in.

So what does this mean?

It means that depending on the Ad Unit sizes you use on your website different
contingents of Ads to display are available.

So let’s do a simple example:
Let’s take one webpage of a website using my Ad Units setup I described above.

Large Rectangle format:

Medium Rectangle:

in real time more competition means higher CPC which translates to higher eCPM
for you as publisher.

By choosing industry standard Ad Unit sizes you increase competition because
more Creatives (Banners) are available for these sizes then for non standard

This is the only way I can explain the discrepancy I see in my AdSense Stats without

In conclusion:
Enabling Image Ads (at least for industry standard Ad Unit sizes) is important to
increase your revenue. And only if you compare Ad Units of the same size or text
only Ads then the fact is true that the first Ad Unit gets the highest paying Ads.

What are your thoughts on this?

I digged even deeper into my stats and now I don’t
know what I should believe anymore at all.

It just came to me that I could compare older stats
of my site from a time where I used a large rectangle

The results are:

The CTR of my 2nd large rectangle was 105% of the CTR
of my 1st large rectangle.

The average CPC of my 2nd large rectangle was 113% of
the CTR of my 1st large rectangle.

The eCPM of my 2nd large rectangle was 120% of the eCPM
of my 1st large rectangle.

This can’t be explained by different contingents of Ads being