Unique Visitors May Not Be So Unique

When website visitors are tracked, either for the purpose of calculating audience size or to keep track of the number of advertisements you are serving, one of the most interesting metrics to look at (at least traditionally) is the number of unique monthly visitors to your content. According to a study released by ComScore today, however, your unique visitors may not be unique at all.

Most services that track web metrics count unique visitors by using cookies. According to ComScore's study, these internal web analytics softwares will on average over-count your audience by 250%. Which means that your audience is actually 150% smaller than you think it is - based on the numbers these analytics packages give you. What's worse is that if you have a technology-savvy audience (i.e. majority of the seo, smo, smm, audience) then your audience maybe overstated by a factor of 1,250% per month! The latter of the two facts is because technology-savvy computer users delete cookies quite frequently and therefore,

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 conclusion, as Fred mentions, we ultimately draw from this is that,

You cannot rely on your own analytics data. You need third party data as well. That's not to say that third party data (primarily panel data) is perfect either. You have to triangulate between all the numbers to get a decent view of what's actually going on.

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M Freitas, April 16, 2007

And of course ComScore offers the "panel data" they refer to in their release, competing with others such as Hitwise (ISP logs) and Nielsen//NetRating (tracking).

Just FUD I'd say...

DrDoubt, April 16, 2007

"According to ComScore's study, these internal web analytics softwares will on average over-count your audience by 250%. Which means that your audience is actually 150% smaller than you think it is -"

thats wrong, it shd be 60 percent less.

doug, April 17, 2007