Cookie Deletion Whitepaper

The Impact of Cookie Deletion on the Accuracy of Site-Server and Ad-Server Metrics: An Empirical Comscore Study

The study addresses the key sources of discrepancy between server-based and panel-based data and reveals that cookie deletion can lead to large overstatements in servers’ measurement of the size of online audiences. Without appropriate adjustments, site server audience reports can be inflated up to 2.5 times the actual number of unique visitors.

• Topics covered in the whitepaper include:Thorough discussion of the study’s methodology.
• Quantification of the degree to which cookie deletion leads to an overstatement in site-servers’ estimates of the number of unique site visitors.
• Comparison of first-party vs. third-party cookie deletion rates and the resulting overstatement in servers’ estimates of the size of site audiences and the reach of online advertising campaigns.
• Examination of consumers’ awareness of, and attitudes towards, cookies.
• Analysis of other factors leading to potentially inflated audience reports from site server data such as failure to remove international traffic from calculation of the domestic audience and the impact of cookie blocking.