Does This Ad Format Reduce Your AdSense Earnings?

Like many publishers we use Google AdSense here at BestTechie as a form of monetization.  And like every Google AdSense user, we receive messages from Google with recommendations on how to help increase our AdSense revenue.  One of Google’s major recommendations that I’ve seen and received, is to utilize their 336×280 ad format.  The larger ad format, which is essentially the big brother to the more traditional 300×250 ad format, supposedly will increase your revenues–I’m guessing because its bigger, not as traditional looking, and more likely to be clicked on.

However, in my experience and after speaking with another AdSense publisher, that wasn’t the case at all.

In fact, in both of our experiments when switching over to using Google’s 336×280 ad format, our AdSense revenue declined greatly.  I used the larger format all through February and had a 24 percent decrease in AdSense revenue for the month.  How do I know that it wasn’t some other factor that caused the decrease in revenue?  Well, for starters, page views and other traffic indicators were up for the month and more importantly, as soon as I switched back to the smaller 300×250 ad format yesterday, ad revenue instantaneously picked back up with an over 200% increase from the previous day.

That trend has continued into today, and will probably remain the case from here on out.  So what’s the deal with the 336×280 ad format?

I have a pretty simple theory: Google’s ad inventory for the 336×280 ad format is much smaller than the more traditional 300×250 ad inventory and that means there’s less selection for it to show, therefore the ads may not be as relevant to the visitor.  Of course, results with using the bigger ad format will vary depending on your industry and niche, so the inventory for 336×280 may work better for some than others.  Nonetheless, this is just a theory, I don’t have any real evidence to back it up (aside from me noticing that the ads being shown on the site via AdSense weren’t that great)–but it does seem that it could very well be the case.

Have you had success with the larger 336×280 ad format or have you noticed less AdSense revenue using it?