Your Best Ad Copy - According to Whom?

By Ammon Brown, Associate Director, Client Strategy & Development

As search marketers, we all know the value in testing ad copies and the importance of the ad copy to the overall performance of your campaign. However, in order to test ad copies we frequently add a number of them to Google AdWords, turn on the ad optimizer, and wait. But is this really the most optimal means of determining your best ad copy? For that matter, what numbers should you look at to compare ad copies?

First, it is useful to know what Google considers good ad copy. Google likes the ad copy that garners the highest CTR. With enough data they will always skew toward that one ad copy that does better than the rest. However, is that in your best interest? If I am a direct response client seeking ROI then this is certainly not in my best interest. A good example of this came up recently while looking through one of our accounts to boost ROI. The account’s ad copy statistics are below:

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Google Ad Copy Results

As you can see, ad copy A was receiving the best CTR, a whopping 21.23%. Ad copy B was “only” getting a 20.77% CTR. Over time, Google had optimized toward ad copy A, showing it 44% of the time and ad copy B only 7% of the time. But look at the conversion rate difference! If we assume the conversion rate would be the same regardless of traffic, we can see which ad copy is really best.

Assume that only ad copy A was in the ad group. The 26,706 impressions would have then received a 21.23% CTR and a 1.77% conversion rate.

    26,706 (B) impressions * 21.23% (A) CTR = 5670 clicks, a lift of 123 additional clicks.

    5670 clicks * 1.77% (A) CVR = 100 conversions, a decrease of 29 conversions!

Now let’s assume that only ad copy B was in the ad group:

    157,021 (A) impressions * 20.77% (B) CTR = 32,613 clicks, a decrease of 715 clicks.

    32,613 clicks * 2.33% (B) = 760 conversions, an increase of 169 conversions!

By removing ad copy A we should in theory receive 715 fewer clicks and 169 more conversions! Of course other factors such as landing page could skew the conversion rate, CPCs may vary slightly by ad copy, and this analysis makes some assumptions that the numbers will remain constant. However, this type of ROI-based analysis still yields measurable incremental gains in many cases.

Be on the lookout for these types of mathematical opportunities. In the example above, Google was optimizing toward delivering the additional clicks generated by ad copy A, regardless of conversion rates. Moral of the Story: You should not always trust Google to make these decisions for you.


Unknown said...

Good post, Ammon.

Although ad B has a higher conversion rate, it has been served substantially less times than ad A so the data is skewed. I'm not sure you can draw the conclusion that ad B is better than ad A just because it has a higher conversion rate.

The only realistic way of determining if ad B is truly superior to ad A is to switch the campaign to 'rotate' ads evenly then compare the data after a set number of weeks.

Good luck!

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