How many ad units? Maybe bid gap analysis helps…
The bid gap analysis provided by AdSenseAccelerator is my favorite feature of the tool, and it occurred to me that the bid gaps might be a good way to decide on how many ad units to display on a given page.
Let me explain. The bid gap refers to the difference between successive bid prices. Here's a set of bids taken from AdSenseAccelerator:
Note the large bid gap between the first and second columns. The gaps get smaller between successive columns. To get 3rd or 4th position for the first keyword, the advertiser only needs to bid around $1.74. But to get 1st or 2nd position, the advertiser needs to bid $3.72 or higher. These numbers are all estimates, of course, and other factors can reduce the price the advertiser pays as well. So these numbers aren't cast in stone. But they're good for judging relative values.
What should interest you is where the bid gap gets smaller, especially when the bid values go lower than $1. If only the top three or four bids look worthwhile, maybe this means you should only show two ads on the page to maximize the chance of your visitors clicking on the higher-priced ads. You can do this in different ways, of course, such as using two half-banner units, a single banner unit, or a short vertical banner.
These are just my initial thoughts, I've started an experiment to see if there's any kind of correlation between the bid gaps and the optimal number of ads to display. Stay tuned!
Eric Giguere is the contextual advertising expert who wrote Make Easy Money with Google and Uncommon AdSense. You can read this blog by mail if it's more convenient for you, just send a blank email to memwg-blog@aweber.com to subscribe.