The choices that other advertisers, who are participating in the same auctions as you, make can affect your campaign’s performance. New advertisers or advertisers who adjust their existing accounts can affect how many impressions your ads receive.
What you can do
If you didn’t make any changes to your account, but there is a large change in Impression share, it could indicate other advertisers have started bidding more competitively in the auctions you're entering in. Consider raising your bid.
Need something else?
Check other common reasons why your campaign performance is fluctuating.
