If you (or your agency) isn't using UTM parameters in Google My Business (GMB) URL fields, you should stop reading this post and add them now. The insight that UTMs in GMB provides in Google Search Console (GSC) is undeniable. If you already have UTMs in place, this post is for you.
One of the biggest misconceptions we run into about GSC data is that it shows a complete picture of a site's impressions, clicks, etc, in Google. It doesn't. This becomes even more of an issue when analyzing URLs with UTMs dedicated to GMB.
First, as previously stated, GSC doesn't show every impression and click for every URL and filters data in a variety of ways. Second, even for the filtered data, there's search flux. Put simply, the results aren't static. Third, Google has made a lot of progress on personalizing and localizing the results. Put simply, a search from X on Y device yields a much different result than a search from A on B device.
The so what is that when you (or more likely your agency) reports on organic performance, it's probably wrong.
Look at the image at the top of this post. If you look only at the Impressions, Clicks, and Positions for the GMB URL, you might grossly misunderstand the performance of your GMB listing for this query in local pack. For example, your agency might say something like:
You're in the number one position in the local pack for this query."- Some Agency
And they're not technically wrong. But they're also not giving close to the full picture. A better way for them to communicate it is something like, "According to GSC data, your GMB listing is averaging in the number one spot for ~ 7% of the reported organic impressions.
In other words, a lot of opportunity for improvement!