Why Google AdWords May Show Lower-CTR Ads More Often

Ad Rotation in AdWords
An important feature for marketers that’s built into Google AdWords is the ability to create two or more ads within one AdGroup and letting Google rotate the ads. Google tracks statistics such as the number of impressions, clicks and the Click-Through-Rate (CTR) over time for each ad so that you can log in after a while and see which ad performs better. As you’re probably aware, CTR is as important as your maximum bid in determining the position of your ad in the search results.

AdWords provides an option of showing the “better performing” ad more frequently. This is found in Campaign Settings under Advanced Options, and is enabled by default. When you look at your ad statistics over a period of time, AdWords will show you the percentage of impressions each ad got. The idea is that the ad that pulls a higher click-through rate will get an increasing percentage of the air play, while the losing ad will show less and less often, which is exactly what both you and Google want.

But it Doesn’t Always Seem to Work That Way
Occasionally we’ve noticed that the ad with a higher CTR gets lower percentage of the impressions. We wondered why and contacted AdWords Support.

First of all, you need to remember that when you set up a new AdWords campaign, there are three places where your ad will appear:

1. Google Search results.

2. The Search Network, which are the search results pages of other search engines that show AdWords ads, including AOL, CompuServe, Netscape, Ask, AT&T Worldnet, EarthLink and Excite.

3. The Content Network, which is any website that’s contextually related to your keywords and ad copy and is running AdWords ads (also known as AdSense).


You can disable your ads from appearing on any of these networks individually.

Turns out the CTR stats that are presented to you on your dashboard are gathered from Google Search and Search Network, assuming your ads appear on both of these. But Google determines ad rotation by the CTR of your ad appearing on Google Search alone. This CTR is not shown anywhere. The only way to find out what it is would be to uncheck the boxes for all other Networks other than Google Search and let the ad run for a while.

The CTR of your ads on the Content Network, assuming your ads are appearing on the Content Network in the first place, does not affect ad position or rotation.

Google Support did not explain to us why ads should have significantly different CTR performance on different search engines, but it probably has to do with the fact that different search engines attract different audiences. Fortunately, in the vast majority of cases, the CTR data presented supports the ad rotation and this is not an issue.

Our Recommendations
So what should you do? Let Google optimize your ad rotations, or figure out which ad is doing better manually by tracking the CTR across Google and the search network?

If they are in synch with each other, which they will be about 95% of the time, you don’t need to do anything special. Just let Google optimize the ad rotations and keep an eye on CTR over time so you can try new ad creative’s.

If the results are out of synch, then you should decide which search engines matter more to you.

For example, if you’re a technology company and figure that your most important audience is highly Google-centric, then just follow Google’s lead and let Google continue to optimize ad rotation. If you periodically try to improve on less productive ad, then the ad that gets a lower percentage of impressions (not the ad with the lower CTR) is the one to replace.

If you sell to consumers and weigh some of the other engines in the Search Network more heavily than Google, then un-check Google’s automatic “show better performing ad” option and do your A/B testing of ads and ad replacements based on CTR.


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