Post by Stu Beurskens, Search Director – Performics Practices Team
On May 15, Google updated its Impression Share calculation to begin incorporating additional search impression data (“log data”) that had not previously been captured in its universe of eligible search impressions. As a result, some advertisers have seen an impact to Impression Share as Google’s definition of marketplace size has expanded with the inclusion of more impression data.
WHAT IS IMPRESSION SHARE?
In paid search, Impression Share is used to evaluate the marketplace opportunity (or consumer demand) for a defined set of keywords. This metric shows an advertiser the ratio of actual ad impressions served for a particular keyword set compared to the total number of ad impressions that were eligible to serve. In short, Impression Share is meant to answer the question: “How often is my ad served when consumers are searching my keywords?”
For example, if a set of keywords had been searched on Google 100 times over a period of time, then its eligible impression count would be 100. If an advertiser had served a paid search ad against 60 of those eligible impressions, then actual impressions served would be 60. As a result, this advertiser’s Impression Share would be 60% (60 Actual Impressions / 100 Eligible Impressions).
WHAT HAS CHANGED?
Per communication with Google, some instances of Impression Share calculations had been under-reporting the amount of eligible impressions in the marketplace (i.e., marketplace opportunity). The Google product update pushed live on May 15 has improved the accuracy of Google’s Impression Share calculation, as it is now accounting for more Search impressions (“log data”) than were previously captured. As a result of this change, some advertisers have experienced a decline in Impression Share due to the increase of eligible impressions now being accounted for.
Quote from Google regarding this product update:
“We make periodic improvements to our estimation of Impression Share. We recently launched a change which effectively added more logs data to our estimate of Impression Share lost due to budget, and thus the universe of total impressions we began looking at increased. Advertisers may see a drop in Impression Share as a result of this change. This drop does not reflect any changes in their ads’ performance.”
If we apply this update to the hypothetical example above, this advertiser may have seen its eligible impressions increase to 150 following Google’s incorporate of additional impression data. As a result, the advertiser’s Impression Share would now be 40% (60 Actual Impressions / 150 Eligible Impressions) instead of the previous 60%.
While advertisers may have seen an impact to their Impression Share as a result of this update, we also want to stress that Google has confirmed there is no impact to actual campaign performance and as such Cost Per Click, Click-Thru Rate, Average Position and other performance metrics will remain unaffected.
WHAT ARE THE IMPLICATIONS?
The most important implication of this update is that advertisers may see declines in Impression Share from historical levels if Google has incorporated additional log data to its marketplace. Conversely, this also means that advertisers may now have access to previously unaccounted for inventory within these marketplaces, as Google’s Impression Share calculation now more accurately reflects total marketplace opportunity in Google Search.
As of early June, roughly a third of Performics clients had seen some level of impact from Google’s calculation change to Impression Share. That being said, even for clients whose campaigns have been impacted, the scope of impact has been relatively narrow as these client’s are seeing a change across only a small number of campaigns.
In order to understand the full extent of the impact to your Search campaigns (if any) and whether changes might be required to account for newly identified marketplace opportunity, please coordinate with your Performics Paid Search team.