Flash cookies get deleted, skew audience stats as much as 25 percent

One of the features app makers and online advertisers rely on is reliable measurement of their audiences and customers. But according to Scout Analytics, a Seattle-area firm that provides behavioral analytics tools for online publishers, audiences may be overcounted as much as 25 percent because of Web surfers who delete Flash-related cookies from their browsers and Flash players, either manually or via tools such as Flash Cookie Cleaner.
“Beyond the fact that unique user counts are overstated 2-4X by tracking devices,” Scout senior VO of strategy Matt Shanahan emailed me after a phone interview, “cookies add additional errors in user counts. In our recent study, deletion rates have approached 7% for Flash cookies and more than 30% for HTTP cookies. These deletion rates further skew unique user count.”
A 7 percent deletion rate can cause up to a 25 percent overcount in audience size, Shanahan told me.
Moreover, he said, Adobe’s upcoming Flash 10.1 player will have a private browsing feature that blocks cookies from being stored on the user’s computer as part of a Flash session. Analysts will probably need to work in a fudge factor to account for uncookied users.
Companies: Scout Analytics