Comscore today released a study which address the key sources of discrepancy between server-based and panel-baed data and reveals that cookie deletion can lead to large overstatements in server logs measurement of the size of online audiences.
According to Comscore, “Without appropriate adjustments, server-based audience reports can be inflated up to 2.5 times the actual number of unique visitors.”
The report, which analyzed behaviors in Latin America (Argentina, Brazil, Chile, etc.), revealed that approximately 33 percent of Internet users delete their first-party (i.e. web site) cookies in a month. Third-party (i.e. ad server) cookie deletion rates are even higher than first-party deletion rates, with nearly 43 percent of Internet users deleting their third-party cookies in a month.