Ad Impressions Must be Backed by Actual Visibility, Warns GfK

Ad Impressions Must be Backed by Actual Visibility, Warns GfK PR Newswire NUREMBERG, Germany, June 28, 2012 NUREMBERG, Germany, June 28, 2012 /PRNewswire/ -- Leading research agency, GfK, today warned that relying on ad impressions alone could be giving an incomplete picture of online campaign performance.