Also known as search IS, search impression share is a metric measuring the percentage of impressions your ads receive compared to their potential impression volume. The formula is naturally quite basic to calculate: impressions you get over total eligible impressions. (For simplicity’s sake, eligible impressions are pretty much just the possible amount of impressions you could’ve got.) 

Eligible impressions are determined by your targeting settings, approval status, and quality score.

In today’s digital marketing since the retirement of the average position metric, impression share is now the metric used to gauge ad positioning. And it’s not just useful per ad; on the contrary, search IS data is available at the keyword, ad group, and campaign levels — and can be used at the product group level too if you’re running a shopping campaign.

Beyond just standard search IS, there’s also variations thereof. For example, “search lost IS rank” shows you how often your ad didn’t show up on searches where it was eligible. This metric is displayed as a percentage of your impression share that was lost due to poor ad ranking (from factors such as a low bid or quality score), or lost due to you having too low of a daily budget.

As far as search IS’s significance, it serves as an ideal signifier for gauging both the competitive landscape and your own ads’ positioning. Otherwise without search IS and its other relevant metrics, the process of identifying deficiencies bogging down your campaign would be more or less like stumbling around in the dark.

By understanding search IS, you’ll have a huge help when it comes to identifying your campaign’s ceiling and navigating how to reach that potential.

How to read search impression share

We’ll start out with what we just mentioned in passing above: “other relevant metrics.”

That is, one of the beauties of search IS is that you can further break it down through related, more granular metrics like IS Lost To Budget or IS Lost To Rank. This means you can go beyond just going “Great, our impression share is 80%, hope we can get it higher!” and blindly throwing fixes at the wall and hoping they stick, to actually inferring why your impression share isn’t higher. From there, you end up way more informed about what’s causing your campaign’s impression share bottom line and can formulate far more comprehensive plans to improve its performance. 

In fact, we think the most helpful way to approach impression share — and the metrics surrounding it — is like a flow chart; start at the top with the most broad information (i.e. search IS) and then work your way down through the more specific, granular metrics as you’re lead that way.

For example, say you’ve launched a search campaign advertising trucks to a large rural county, but conversion volume isn’t hitting the point you want.

To examine why, you start at the top: the most basic level of just search IS. You see that’s at 80%, which is actually a pretty healthy number and tells you you’re actually capturing a good deal of available traffic. So what’s next?

You can move down to the next level of metrics. Maybe you see that IS Lost To Rank is showing 50%, which is a lot — now you know that of your lost impression share, half of it is due to being ranked poorly. A look at Top of Page Rate — how often your ad displays at the top of the search engine results page — could confirm this. So now you have two underlying metrics showing you that your ads are capturing a good deal of traffic, but they’re not really placed in those high-converting positions up top. (Sidenote: the first and second paid search results almost always see higher conversion rates.) Now you know what to work on to hit your conversion goals!

In the end, search IS metrics come in many forms and can rightfully be a bit confusing to the uninitiated. We think a great way to approach them is to just keep things simple and clean. Identify your key search IS metrics — we like standard IS and IS Lost To Budget/Rank — and focus your attention there, and you should be golden; in most cases, those three can tell you exactly what your search campaign needs.

This approach to search IS can be really fantastic. Now you have a complex, useful tool at your fingertips utilized in a way where it’s accessible and user-friendly. The end result is the ability to boost your campaigns without too much effort thanks to easily-attained, extremely valuable insight.