Impression share, the percentage of impressions a campaign received out of the number of impressions it could have received, is an important metric advertisers have used in the Adwords account for a long time now at campaign level. There are many reasons a campaign may miss out on impressions, the main two reasons being budget and rank.
It is very useful to monitor these metrics, especially the Lost IS (Budget). This shows what percentage of impressions your campaign did not receive because of budget restrictions. If a campaign is showing a level of lost impressions, the advertiser can then decide what changes to make to improve performance, either reducing bids to get cheaper clicks for the same budget or increase the budget.
According to the Google Adwords blog, the impression share metrics will soon be available at ad group level. The Lost IS (Budget) will not be available as budgets are not set at ad group level, but we will be able to see the impression share, lost impression share due to rank and exact match impression share. These three column options will soon start to show in Adwords accounts at ad group level.
Exact Match IS and Impression share have been available through the dimensions tab previously but we will soon be able to see all three in the ad groups tab.
This will give us more insight into where a campaign is losing out on impressions. We will be able to see if a very strong performing ad group is missing out on impressions compared to other ad groups in the same campaign, and make adjustments to improve the performance.
Once this becomes available I will use it to see how I can make improvements to ad groups and will report back any findings in a future blog post! – @aimee_roberts