While publishers having noticed fluctuating number of ads in ad units that show multiple ads since August 2005, beginning in December the Large Rectangle (336×280) ad unit began showing two ads instead of four with increased frequency. So increased, in fact, that you would be hard pressed to find a large rectangle ad unit showing anything other than two ads at the moment.
Officially, this is called an expanded text ad, since the ad being shown are expanded in the ad unit. I have always referred to these as optimized ad units, since AdSense is automatically optimizing these ad units to show ads that will make the publisher the most amount of money.
I caught up with AdSenseAdvisor (an official Google AdSense Support Team member) today to get the nitty gritty on the whys and hows of the large rectangle showing primarily two ads now. My questions are in bold while AdSenseAdvisor’s answers are in italics.
Why are the large rectangle ad units showing two ads now instead of four? There has been a lot of discussion about this, particularly in regards to earnings.
If you only see two ads in an ad unit appearing, it is because our technology has determined the publisher will receive a higher eCPM. This is an automatic optimization feature.
We think some of the reportedly lower earnings are probably seasonal. However, as always, people should email email@example.com if they feel there is a problem on their particular site.
I have not seen a single ad unit in that size running four ads for weeks now – all are running two ads only. Are the vast majority (or all?) of these ad units only showing 2 now?
No, it’s on a dynamic system. In general, many sites seem to perform better with expanded text ads. However, some sites are still receiving 3 or 4 ads because on those particular sites, the eCPM is higher with more ads.
Is this determined on a per account, per site, or per page basis?
Per page basis.
It is also worth noting that expanded text ads can also appear as a single ad in an ad unit built for multiple ads, and these are still CPC ads, not the site-targeted ads that appear on a CPM basis.
So the bottom line is that these ads are appearing because they will make a publisher more money on the page they appear on. And they do affect other sizes of ad units as well, not just the large rectangle. But it seems that it is the large rectangle everyone is buzzing about. It will be a little more difficult to actually judge if these ads are making more money or not, because they began in December when publisher normally see skewed earnings because of the holidays.
Optimized ad units are all automatic, so you can’t “force” more ads to appear, if you prefer to show more ads in the ad unit. So there isn’t a hidden tag publishers can add, or an account setting to change. AdSense will continue to automatically chose what is more profitable for each page, whether that is 2, 3 or 4 ads in an ad unit.