Anne wants to use her impression share metrics to optimize her Shopping campaign. She should run an Auction insights report to compare her impression shares to those of her competitors
Explanation: The Auction insights report for Search campaigns provides 6 different statistics: impression share, average position, overlap rate, position above rate, top of page rate, and outranking share.
Average position is a quick way to gauge how high your ads are ranking compared with those of other advertisers competing in the same auctions.
In the Auction insights report, impression share also tells you the impression share of other advertisers as a proportion of the auctions in which you were also competing.
Read more here: https://support.google.com/adwords/answer/2579754