Independent Auditing of Online Display Advertising Campaigns

The reported lack of transparency of the online advertising market may seriously affect the interests of advertisers. In this paper, we present a novel methodology that allows advertisers to independently assess the quality of display advertising campaigns. This methodology also serves to audit the accuracy and completeness of reports delivered by the vendor responsible for running a campaign. We have applied our methodology in 8 display ad campaigns configured in Google AdWords, which overall produced 160K ad impressions displayed in more than 7K publishers. Our results reveal that AdWords seems to provide incomplete information to advertisers. Specifically, we found that: (i) AdWords did not report 57% of publishers where ad impressions from our campaigns were delivered, (ii) AdWords reports a large fraction of contextually meaningful impressions based on (non-disclosed) criteria different from the publisher’s theme, (iii) higher CPM investment does not lead to get impressions delivered to more popular publishers, (iv) AdWords does not offer default control of frequency cap, (v) around 10% ad impressions in two of our campaigns were delivered to IP’s from Data Centers. The industry considers these IPs to be likely related to fraud. These findings should contribute to open a debate between advertisers and Ad Tech vendors to standardize the utilization of independent auditing methodologies as the one presented in this work.