As is the case with many AdWords features , Google’s impression share report is a powerful, useful, but incomplete and potentially misleading tool for AdWords advertisers. There are two major issues with taking impression share reports at face value:
- You don’t always want all the impressions
- A small percentage of a large campaign can be much more impactful than a large percentage of a small campaign
In any PPC campaign there is a concept of diminishing returns – just because you can get x conversions at y price per conversion doesn’t mean that if you get 2x the conversions your cost per conversion will hold – in fact in a vast majority of cases it won’t. For this reason there are many instances where even if your campaign is profitable and you’re only capturing 40% of the possible impressions, you wouldn’t want to increase your budget or your bids to get all of the possible impressions.
The second issue with the impression share report is that a percentage of possible accessible impressions isn’t always the most useful and actionable data. This is because the percentage doesn’t take into account the actual impact of the additional impressions. For instance, if you have a campaign that is targeting a broad array of possible keywords, is highly profitable for you, spends 80% of your budget, and is only accessing 80% of the universe of possible impressions, that’s far more interesting than a campaign that spends 1% of your budget, wouldn’t be profitable if it expanded any further than it already has, and is intentionally targeting a narrow sliver of the possible keywords in that keyword niche that has 30% of impression share. But the flat impression share report makes this second metric look more alarming and gives the impression (no pun intended) that there is a lot more opportunity inherent in that number than there really is.
Weighted Impression Share Reports
WordStream’s relatively new Google AdWords Performance Grader  is a free tool that includes an enhanced impression share metric – it layers budget data on top of impression share to offer a global metric rather than a “flat” impression share percentage applied to disparate data points (i.e. higher and lower budget campaigns). Instead, you get a more authentic view of the actual share of voice you’re sacrificing based on the relative share you’re accessing based on the budgets allocated to the different campaigns. You then get the same breakdown of share lost to budget/share lost to ad rank offered by AdWords, but with a more meaningful representation of your actual share of voice.
Additionally, another layer of context is placed on top of this as the report “scores” your impression share relative to advertisers spending similar amounts per month on AdWords. This helps advertisers understand how many value-added impressions they’re sacrificing, and helps them understand how that relates to similarly sized AdWords advertisers. By understanding these metrics they can then have a better grasp on what types of opportunities they’re leaving on the table, and in turn make smart decisions on how much and where to push additional budget and increase bids.
You can find out how your campaigns stack up, in terms of impression share as well as other key metrics like Quality Score and click-through rate, by running your own AdWords Performance Grader report .