Q: What Is Search Impression Share and Why Is It Important?
A: Search impression share is a percentage that indicates how prominent your ads are on the search engine results pages (SERPs) based on the keywords you are currently bidding on. It is calculated by dividing the impressions you have received by the total number you were eligible to receive based on your current keywords, bids, settings, etc. For example, if you have a 75% search impression share, you are missing out on 25% of the impressions you were eligible to receive.
The next natural question of course is, how can I obtain those missed impressions? Fortunately, Google shares two additional metrics that help indicate just that. Search Lost IS (Budget) and Search Lost IS (Rank).
Search Lost IS (Budget)
Search Lost IS (Budget) is an estimate of how many impressions you are losing based on a budget that is too low. Raising budget (and not altering anything else) is generally a very easy way to gain impression share quickly. That said, if you are losing impression share due to budget, you can use your campaign data to determine exactly how much budget you may need to add to get this metric to 0%. This can be done in 4 easy steps.
Step 1: Find eligible impressions by using the following calculation: Impressions / Impression Share.
Step 2: Find incremental impressions by using the following calculation: Eligible Impressions * Lost IS (Budget).
Step 3: Find incremental clicks by using the following calculation: Incremental Impressions * Stable CTR.
Step 4: Find incremental cost by using the following calculation: Incremental Clicks * Stable CPC
The incremental cost is how much additional spend you should add to reach a Search IS (Budget) of 0%.
Search Lost IS (Rank)
Search Lost IS (Rank) is an estimate of how many impressions you are losing based on your Ad Rank. Ad Rank gets calculated for every auction and ultimately determines the position in which your ad is shown (or shown at all). Below are all considerations that Google uses in determining Ad Rank.
Bid – What is the max you are willing to pay for a click?
Quality Score – How relevant are your keywords to a user’s search? Do your ads and landing pages align with what users are searching?
Context of the Search – What were the search terms they entered? What device were they on and where were they located? More and more signals are being taken into consideration today more than ever.
Ad Extensions & Ad Format – Are you taking advantage of ad extensions that can better the users search experience? Google Ads takes into consideration the usage of ad extensions and the impact that has on overall performance.
All in all, Search Impression Share is important because it gives insight into campaign health. It’s a great way to determine if you are missing out on impressions due to budget as well as the overall quality of your campaign structure, keywords, ads and landing pages.