Google said on Tuesday that beginning later this month, AdWords will begin rolling out a new calculation for impression share. This will affect reports in the AdWords API if you're relying on impression share columns and run Video Campaigns.
The roll out will occur over the next few months for all accounts and impressions. Google says if you run campaigns on YouTube, your impression share stats will become more accurate when your account goes live.
"Historically, a small percentage of impressions on YouTube videos were not being included in the calculation of the impression share columns," explains Michael Cloonan from Google's AdWords API team. "We've implemented an improved algorithm to more accurately count impression share volume that now accounts for these impressions."
Issues can be reported in the forum here.
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