Tuesday, April 17, 2007

Pass me the cookies - but please do not delete

US online measurement company ComScore sent an out an interesting press release yesterday which questions the use of cookie-based data to determine the number of unique visitors to individual websites.

[Cookies are what Wikipedia calls "parcels of text" sent by a browser to authenticate and track users]

Apparently 31% of US internet users clear first-party cookies - those sent direct from websites - out of their systems every month, meaning that if a site uses the number of cookies it sends out as a basis to work out traffic levels it might actually be over-cooking the figures - slightly.


There's more: the sample size for the study was 400,000 home PCs and the average number of cookies each had for a single site was 2.5.

ComScore says:

"This indicates that website server logs that count unique cookies to measure unique visitors are likely to be exaggerating the size of the site’s audience by a factor as high as 2.5, or an overstatement of 150 percent." That suddenly sounds like rather a lot...

For third party cookies, those which are often sent via advertisers on a website, the figure is even higher at 2.6 per user.

Would be intrigued to learn if any travel sites are still using this method to establish their traffic figures.

[Full release here]

Kevin May, editor, Travolution

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Craig McGinty said...

Hi Kevin
I notice you are keen to learn about compaines who "are still using this method" I'm not sure there is any other way at the moment???
Considering the innovation elsewhere on the internet the stats side of things is still lacking.
There are so many conflicting standards, marketing smart workarounds and plain old confusion I think people don't know there stats from their hits - you might say.
I've always thought the Audit Bureau of Circulation could have led the way in this area to work say via an open API that could become the de facto method, maybe that's just wishful thinking.
All the best

Steve E said...

As Craig says pretty much everyone will be running stats using cookies.

The bit that has always confused me is that the big analytics vendors always try to tell you that 1st party cookies make a huge difference. I've always been skeptical as most users who delete cookies will delete them all and not differentiate between 1st and 3rd party.

Paul Goodison said...

Steve - I think its more that users tend to block 3rd party cookies at presentation but are more liekly to accept 1st party.

On the whole issue I tend to look at overall trends anyway rather than specifically at numbers

Travolution Blogger said...

Craig, Steve and Paul: thanks for the comments. cedrtainly something we should look into for a future edition of Travolution, especially with regards to travel websites.

Steve E said...

Paul, of course you're right, but the same goes as I don't know anyone personally who only accepts 1st party cookies (and I know a lot of web people).

You're definitely right to look at overall trends, I don't know of a single stats package that you could call totally accurate. Even web logs won't gather all the information you need from all of your users.

It would definitely make an interesting feature for a future edition. It would also be really interesting to hear how the top analytics companies are going to continue justifying costs of up to (and in some cases more than) £20k per annum when Google Analytics is free. I know they offer more functionality, but is it really £20k's worth?

Paul Goodison said...


Check out Internet Explorer Privacy Settings - you might not explicitly block third party cookies but allegedly MS does it for you!

Firefox doesn't have anything similar.

And ditto on the analytics packages - to me they all end up being stats production rather than analysis, which is where I would like to see the value add.

Steve E said...

Good point Paul. However on Medium privacy setting (which I believe is the installed level) it only blocks 3rd party cookies which don't have a compact privacy policy, or that collect contact info. The Urchin cookie with Google Analytics does have this privacy policy as do most other stats packages and they don't collect contact information so should be okay (in the majority of cases). Of course this does mean that some will get cleared out by users who go for higher levels of security so cookie based tracking will never be 100% reliable.