Have you ever been suspicious that your traffic stats are overinflated? Well, you should be, especially if you use cookies to track user analytical data. According to a new press release by comScore cookie-based counting overstates the size of a web site's audience.

"While past studies from other research companies have shown a similar proportion of computers that clear their cookies, the comScore study is the first to highlight the disproportionately high percentage of cookies represented by those computers,” commented Dr. Magid Abraham, President and CEO of comScore. “For example, with just 7 percent of computers accounting for 35 percent of all cookies, it’s clear that a certain segment of Internet users clears its cookies very frequently. These ‘serial resetters’ have the potential to wildly inflate a site’s internal unique visitor tally, because just one set of ‘eyeballs’ at the site may be counted as 10 or more unique visitors over the course of a month. The result is a highly inflated estimate of unique visitors for sites that rely on cookies to count their audience.”

The problem is people like me who routinely clear their cookies out of their machine. I clear them out monthly but some of the more obsessive-compulsives in the online world clear their cookies weekly. In either case, these routine deletions are creating over-inflated traffic counts.

“In 2005 while at JupiterResearch, I reported the results of a survey showing that 39 percent of Internet users claimed to delete their browser cookies on a monthly basis,” said Eric T. Peterson, well-known web analytics consultant and author of “Web Analytics Demystified.” “The data from the comScore study, especially the findings regarding first-party cookies, clearly highlight the risk to cookie-based measurement. The comScore study emphasizes that site operators need to be extremely careful when calculating and reporting unique visitor counts from server log data, questioning both the technology they use and their underlying assumptions about cookie deletion rates among their site visitors.”

If you're using a cookie-bases system for your analytics, it might be time to reconsider your options. Especially if accurate traffic reporting is important to your marketing team.

As Bruce Almighty would say, "...and that's where the cookie crumbles."