While it was no secret that counting website visitors is notoriously inaccurate, comScore has released a study that indicates cookie tracking can over represent your visitors by a factor as high as 2.5.
Some interesting highlights in the article:
- 7% of computers account for 35% of all cookies
- 31% of Internet users cleared cookies during the month of the study
- Only 4% of Internet users delete third-party but not first-party cookies
- Traffic overestimation can be up to 150%
This is interesting because many online tools such as Google Analytics (which I use) leverages cookie track visitors. This is an example of a “third-party” cookie. The cookie is used to track when a visitor returns.
There is some good news: If this is the case, return visitor rates may be far higher than what is reported. Cookies are used to track return visitors, so if those cookies are getting wiped out, using the same logic, I can conclude my return visitor rate may be up to 2.5x greater.
The alternative is to use server side tracking such as Awstats, or some combination. In reality, I don’t really care how many visitors I have, but it’s still an important thing to keep in mind.