Keyword Cannibalization happens when a search query is matched to more than one keyword(s). It results in the matching keywords competing with each other. Depending on the Quality Score and bid of the keyword, Google then ascertains which ad to show. Such a scenario leads to uncertainty in determining whom to consider as the one triggering performance.
Cannibalization is more likely to happen when you have added similar keyword in your campaign but with different match type. Here is an example of such an arrangement:
In the above example the search query triggers more than one keyword leading to the behaviour of keyword being unpredictable. You would not be able to ascertain which keyword will perform when. This might also increase the chance of an irrelevant ad being shown instead resulting in drop in conversions. The pattern can overturn in some cases where the traffic is relevant and results in conversion. So, basically you lose control on how a keyword will react.
Here is a detailed post on how to Avoid Keyword Cannibalization In Paid Search Campaign.
Further you can get hold of our ‘Cross Ad Group Impressions‘ Report which gives access to data of the multiple keywords being matched to a single search query across different ad groups. This is generally undesirable because it means your keywords are competing with each other, thereby raising the CPC. It also is sub-optimal in case, you intended the search query to match in a specific ad group where you have crafted a custom ad and landing page. You would like all the traffic for that search query to go to that specific ad group. That is if your search query is “nike running shoes” you would like to match in the ad group about “nike running shoes” and the generic, catch-all “nike shoes” ad group.
Here is how the report appears:
As in the above snapshot, you get summarized information of each search term that is getting mapped with the keyword from your campaign. Also you get all the details of the performance metric to help determine if you are loosing out on money or getting valuable traction.
To get this report, register for our Negative Keywords Tool for free and access the data hands down.