Search Impression Share (SIS) allows marketers to compare an ad campaign’s impressions to the total possible impressions that campaign is eligible for. Tracking this metric over time can provide a deep understanding of how successful a campaign (along with its ad groups and keywords) is in terms of reaching the largest audience possible. Essentially, SIS gives the return on opportunity cost for an ad campaign.
Impression Share eligibility is regulated by factors such as budget, keyword selection, audience targeting, region, and timing. Although it is desirable to win a large percentage of the possible Impression Share, high SIS does not necessarily result in conversions or ad clicks. Therefore, it is important to track SIS alongside Ad Clicks and conversion rate.
