PPC & KPI Monitoring: How to Diagnose Lost Search Impression Share Rank & Top Impression Share Changes

By Brad


General, Performance Analyzer

In our continuing series on KPI Monitoring & Diagnosis, today we’re going to dig into examining changes to Impression Share Lost due to Rank and Top Impression Share Metrics.


These two metrics are highly related as having a high absolute top impression share percentage or a high top impression share percentage is directly related to having a high ad rank. As ad rank falls, you often see a drop in your top impression share metrics and an increase in lost impression share due to rank.

This is not absolutely correlated as you can have a slight ad rank drop and fall to the bottom of the page, but you’re still on the page. In that instance, you’ll see a decline in top impression share but not a drop in lost impression share due to rank.

To understand ad rank and diagnose this metric, we need to first look into what makes up ad rank.

How Ad Rank is Calculated (The Simplified Version)

Every time someone searches, Google determines all the eligible advertiser’s ad ranks. They then order the ad positions based upon everyone’s ad rank. Your ad rank only matters in perspective to the other advertiser’s ad ranks. Ad rank is calculated based upon three variables:

  • Your max CPC: What are you willing to pay for a click
  • Your auction Quality Score
  • Your ad extensions impact on CTR for that auction

As these three items change, it affects your ad rank and therefore, your ad position.

If your ad rank is too low for your ad to be displayed on the page, then you lose that impression due to low ad rank.

Google shows you this number in the metric: Lost Search Impression Share (Rank). This is also called Lost IS (rank).

To understand why we’re losing impressions due to ad rank and why this number changes over time, we need to dig into these three factors.

Changes in Quality Score

Your Quality Scores are always in flux. As your website changes, ads change, ad group organization changes, then your Quality Score will change. If users click on your ads at differing rates, then your Quality Score can also change as CTR is a component of Quality Score.

The easiest way to diagnose changes is to trend your Quality Scores over time.


In this case, an advertiser had launched a new product. The organization was good for that campaign (hence the high ad relevance), but the landing page and CTR needed help. They did some landing page testing and a lot of ad testing, and in the course of a few months, their Quality Scores went from a 5 to a 10 for these new words.

If you see changes to Quality Score, these often have a direct impact on Lost Impression Share due to Rank.

If you need some Quality Score resources, these will help you increase your Quality Scores:

Max CPC Changes

What you are willing to pay for a click is a massive component of ad rank. If you make significant changes to your bids, then you’ll see changes to your Lost Impression Share due to Rank. You should also see changes to your Top and Absolute Top impressions and impression shares.

If you are manually bidding, then you should have a good idea of significant bid shifts.

If you are using enhanced CPC or automated bidding, then you might not see these changes as Google Ads or Bing Ads is changing the bids on your behalf and it’s easy to miss some keywords suddenly getting fewer impressions. Watching your average CPCs over time can help you see any changes the automated bid systems are making to your bids to see if you suddenly start losing impression share.

If you switch bid methods, this can also affect your lost impression share due to rank since the new system might make substantial bid changes.

Changes in bids that caused ad rank to drop (look at CPCs and so forth)

Targeting Methods are Changed

You can look at Lost Search Impression Share (rank) for all your search campaigns, a single campaign, an ad group, or individual keywords. If you are looking at a level, such as all search campaigns, and you have changed the targeting options by:

  • Adding keywords
  • Pausing keywords
  • Adding negative keywords
  • Removing negative keywords
  • Changing match types
  • Adding or excluding audiences
  • Adding or changing time of day, demographic, or other settings

Then your Lost Search Impression Share (rank) will most likely change. If you launch several new ad groups and you see your Lost Impression Share (rank) change, then you’ll want to look into those new ad groups as odds are, they are playing a part of your changes.

Ad Extensions

It is essential to use the recommended amount of ad extensions as these play a pivotal role in ad rank. It is common for a campaign to miss an extension or two (this is easy to diagnose), and adding those missing extensions can help mitigate impression share loss due to ad rank.

If you add new campaigns, ensure you are using all of your ad extensions properly.


Graphing Top Impression Rates

When it comes to digging into changes to your top & absolute top impression rates, it’s useful to graph them out over time. This will let you see those changes so you can isolate the time frames for changes to diagnose the changes.


There are many ways to graph top impression rates from time to CPA, CPC, Conversions, versus Impression Shares, and other methods. This will help you see the trends in your top impression numbers and compare them to your Quality Score graphs and CPC graphs to understand why your top impression shares have changed.

Wrap Up

When your Lost Search Impression Share Rank or your Top and Absolute Top Impression Share metrics change, there are four primary ways to dig into the data.

The first is graphing your Quality Scores over time to see if a change in Quality Score affected your impression shares.

The second is to examine CPC or bid method changes to see if your CPC has changed and that affected your ad ranks.

The third is to look at any new targeting methods or changes in targeting methods from keywords, audiences, time of day, demographics, and other targeting options.

The fourth is always to make sure you have the recommended number of ad extensions.

By looking into these four items, you can diagnose why your Lost Search Impression Share Rank or Top Impression Share metrics changed. This information will help you put a fix into place to ensure you are always showing your most profitable ads.

To learn how to monitor KPIs and diagnose other data changes, please see our KPI Monitoring & Diagnosis series.

To quickly create these charts and get automated KPI monitoring for your account, as well as a considerable amount of other PPC management features, you can take a Free Trial of Adalysis.

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