Google now has a new top ad placement formula. They say it is an improved formula used to determine which ads are placed in the top spots above Google search results.
Google also says the change gives advertisers more control over when their ads reach the top placement and increases the quality of the ad results for users.
A big change is how price is considered. The maximum CPC of an ad is now considered while it previously was the actual CPC. The way it is done now for the top spots is like the formula used for ranking ads alongside Google search results.
This link is to the official details from Google
Inside AdWords: Improved top ad placement formula now in effect
New top ad placement formula
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