PPC & KPI Monitoring: How to Diagnose Changes to Your Impression and Search Volume

By Brad


General, Performance Analyzer

In our continuing series on KPI Monitoring & Diagnosis, today we’re going to dig into examining changes to impressions and search volume and what leads to these changes.

To arrive at these metrics, we’re using some basic math.

Impressions are the number of times your ads were displayed by the level you are looking at (account, campaigns, ad groups, etc.) within a timeframe.

Impression share is the percentage of times your ads were displayed when they were eligible to be displayed. For today’s purposes, we’re going to focus on search.

Search volume is the total possible search volume for that level and timeframe. Search volume is arrived at by examining the impressions you received and the search impression share to determine the total search volume.

We then compare this data to another timeframe to see how these metrics have changed over time.


There are four quick questions you want to ask yourself, so you know where to start looking into the data:

  • Did impressions go up or down?
  • Did search volume go up or down?
  • Did search volume go up or down at a higher ratio than impressions?
  • Did impressions go up or down at a higher ratio

Let’s dig into these scenarios to start examining the root causes of what to look for in your diagnosis.

Impressions or Search Volume Increase or Decrease Significantly

If impressions go up or down significantly, the most obvious question to ask is, did you just enter or leave a peak period? As seasonality significantly affects total impressions or volume, this might just be a seasonal change. If it is a seasonal change, you often want to do year over year trending to see how that season compared to the previous season.

If that is not the cause of the change, then let’s look at the other factors that affect impressions.

Budgets & CPCs: Did your budget or average CPC go up or down? A change in budget can affect how many clicks you get and therefore, how often your ads show. A change in CPCs can cause impression changes. If you raised your CPCs without changing your budgets, then you can spend your budget faster, and your impressions will go down. As there’s a lot to these two metrics, we’ll spend an entire future article digging into budget and CPC changes and how that affects your impressions.

Targeting changes: did you change your targeting methods or options? Outside of seasonality, this is the most common reason for impressions changes.

Position changes: changes to average position, CPCs, quality score, and top impression rates can cause your ad to drop off page 1 and thus lower your impressions.

The primary targeting changes to examine are:

  • Negative keywords added: reduces impressions
  • Negative keywords removed: increases impressions
  • New keywords added: increases impressions
  • Keywords paused: reduces impressions
  • Match types changed: can increase or decrease impressions based upon if you made them more restrictive or broader
  • New targeting added: this can range from DSAs to new audiences and so forth
  • PPC engines change the keyword matching rules. When the engines change the rules, this can change a lot about your account.
  • Search query changes: You might not change the match types, but suddenly Google or Microsoft matches you to new search terms that can increase your impressions

Position Changes are primarily driven by:

  • Quality Score
  • Average CPC
  • Ad extensions

These metrics are interwoven with some other data, such as CTR, organization, and so forth, we’ll examine these changes in a future article.

If you’re not sure what changes you made, you have a few options to dig into this change data:

  • Drill down into the account in your comparison to find out where the significant impression changes happened. For more information on this, scroll down to the section titled How Much of Your Account Should You Compare on this page.
  • Examine the change history report to see if you can spot the targeting changes.
  • If you keep notes on changes, review your notes or project management system

Once we can see where these changes happened and what did change, we then want to see how it affected our conversions. For example, in this account, the impressions went up 16%, but the conversions went up 49%:


This means we want to look at where the changes came from and see if we can get more impressions. If we see that the impressions went up and the conversions went down, then we usually want to remove the new targeting options that were added as they are not converting.

In other cases, the impressions might have increased at a higher ratio than the new conversions. This is common when adding DSAs or broad match terms. It’s not a bad thing; it just means you need to watch your bidding, so your CPA and ROAS stay in alignment with bidding the new targeting methods differently than your old targeting that had a lower CPA than the new options.

The Ratio of Search Volume to Impressions Changes Significantly

When you see your search volume go up much faster than your impressions, that means that one of your lost impression share metrics is increasing.

Lost Impression Share (budget)

For example, if you are budget capped and you added new targeting methods, you’ll often see an increase in search volume, but a static number of impressions. What will happen is that your lost impression share (budget) increased. In this case, you usually want to look and see if these new methods are converting as well as the old ones, and if so, then raise your budgets to capture these new potential conversions.

Adding new targeting methods when you don’t add new budget (and you are already spending your budget), usually doesn’t affect your impressions that much, it just moves some of your older impressions to new parts of your account.

Another possibility is that there is an increase in search volume (some type of seasonality, promotion, etc. that caused more users to search) and you didn’t increase your budgets enough to capture this demand. Watching the ratio of search volume to impressions along with the changes to conversions and CPA can help you change budgets to capture additional demand for your products and services.

If your impressions go up faster than your search volume, then you’ll see a decrease in lost impression share. If you raised your budgets, you’ll usually see lost impression share budget decrease and impressions increase.

Lost Impression Share (Rank)

If your search volume goes up, but your impressions do not, and you see an increase in lost impression share rank, then you usually want to dig into your CPCs, position, and graph your quality score.

If your impressions go up faster than your search volume and you didn’t change budgets, then your lost impression share (rank) usually decreases. This is often due to raising bids to increasing quality score.

As each impression share loss is its own diagnosis, we’ll dig into each one of these individually in future articles.

Wrap Up

The start of all KPI monitoring and diagnosis is first looking at how often your ads were served (impressions) and their entire potential to be served (search volume). You’ll then want to compare these ratios with each other to see if one is changing faster than the other, and if the changes are positive or negative.

Next, you’ll want to compare with your total conversions to see if the changes to impressions and conversions are roughly the same. If your impressions go up faster than your conversions, the new targeting methods aren’t as good as your old ones. If the impressions go down and your conversions go up, the changes you made are highly positive.

By examining the ratios of search volume to impressions to conversions (and/or revenue) that let you quickly see how any changes you made or changes to search volume are affecting your account. By then understanding how to examine these ratios and what affects the numbers lets you quickly diagnose what happened and then make any appropriate changes to get more of the good, remove the bad, or be happy with the results of your changes.

These ratios are a great starting place. However, they are profoundly affected by impression share numbers ranging from impression share the impression share loss metrics. In our next article, we’ll start digging deeply into the impression share loss metrics, so you know how to evaluate and react to any changes.

To stay tuned to these articles and more, you can subscribe to the Adalysis blog here.

We hope you’re enjoying the series 🙂

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