Impression share is a critical metric for understanding your Google Ads performance. It shows how often your ads appear and provides valuable insights for optimization. However, when you run Performance Max (PMax) alongside Search campaigns, your Search impression share data becomes less reliable. In this article, we’ll explain how PMax affects this data and share strategies to mitigate the effect.
Impression share (IS) is one of the most useful diagnostic metrics in Google Ads. It provides a clear view of your account’s performance and opportunities for improvement. By analyzing impression share, you can:
You can analyze impression share data by keyword, ad group, or campaign. A quick review of the data can help you gain more impressions with your current targeting methods.
Impression share is the percentage of times your ad was displayed compared to how often it was eligible to be displayed. However, there are some important caveats to understand before interpreting this data. This information comes from Google’s impression share help files.
1. Impression share is only counted if your ad is eligible to show.
2. Impression share is only counted when your ad is competitive enough to show in an auction.
If PMax shows an ad over your Search campaign, then Search isn’t eligible for the auction. This was confirmed in a LinkedIn discussion with Google executive Bryan Halicki.
As a result, your impression share data is recorded for PMax, not Search. However, with PMax, you can only see campaign-level impression data — not keyword-level.
If PMax shows over your Search keyword, that means your keyword doesn’t receive an impression and, therefore, no impression share.
Just because PMax can show an ad (meaning it was eligible and your Search campaign wasn’t) doesn’t mean it will. You’ll lose not only the potential impression but also the reporting for that keyword.
This affects many companies that watch impression share for specific keywords:
Some Google Ads managers see their impression share increase while getting fewer Search impressions. While that may seem surprising, there’s a simple explanation:
To recap, impression share is the ratio of how often your ads are displayed versus how often they can be displayed. If PMax reduces your eligible impressions, they’re not counted in your Search impression share.
However, the most common reason for a higher impression share is a “max” bid strategy (clicks, conversions, or revenue). Since Search spends less budget on lost impressions, the bid strategy can increase your bids and lower your lost impression share.
This creates a situation where you can get fewer impressions and a higher impression share. (While that’s the most common scenario, there are many others.)
It can be confusing when Search campaigns have fewer conversions and an increase in impression share due to PMax. In an ideal scenario, PMax obtains the lost conversions, and the account doesn’t see a net loss.
In reality, PMax has a worse conversion rate than Search. Therefore, when impressions move from Search to PMax, the account often loses conversions overall.
To track impression share accurately, it’s essential to add your top search terms as exact match keywords. This simple step will help you prioritize Search over PMax, safeguard your IS data, and ensure your account’s success for those search terms. (You can see the full research and process here.)
Impression share is one of the best diagnostic tools available. Ensuring your data is accurate will give you a considerable boost in determining the best strategies for capturing impressions and growing your account’s conversions.
Further reading:
Todd
Thanks Brad! This explains exactly why the impression share indicates there are only about 10% of the available impressions we had in our Brand campaign before moving it from our main account to our client’s Google Grants account. The main account’s PMAX campaign has taken over most of the brand search volume that the search campaign used to own when it was in the same account.