Calculating Number of Users Based on Amount of Unique IPs?

pjdepasq asks: "I run a small but growing web site. Currently the site has optional registration (for the message boards), though we know we have a larger number of anonymous users. Is there an industry standard for calculating number of unique users based on the unique IP addresses over a period of time (1 week? 1 month?) We'd like to get a handle on the number of users we have. Sure, I know about dynamic IP addreses and ISPs like AOL which can dilute or confuse the numbers, but surely there's some benchmark calculation we can use."

Comments

Re:No!

[Jamie Zawinski]

These problems are not really new to the web -- they are present just as much in print media too. For example, you only know how many magazines you've sold, not how many people have read them. In print media we have learnt to live with these issues, using the data which are available, and it would be better if we did on the web too, rather than making up spurious numbers."

But I'm told by people in the magazine business that the industry standard there is to assume that the number of readers is 5x the number of issues sold. Of course that will vary widely by magazine: but that's the ratio they all use when making readership claims in their rate cards.

This is exactly the question the original poster was asking, but for the web: everybody knows that getting an exact answer is impossible, he's just looking for a rule of thumb.

No!

[Stephen]

I am almost certain that there is no industry standard.

One problem is that it would depend very much on the type of website and thus the type of users you had. If you have a B2B website, and most of your visitors are from companies, your (unique user):(unique IP) ratio will look very different to a site with mostly home visitors coming through large ISPs.

The industry seems to be more concerned with developing more and more reliable versions of the half-hour timeout metric. Of course, they're chasing the wind. (And furthermore, all the different versions of their metric are then not comparable -- see this study from Xerox PARC (PDF, 228kb).)

I leave you with this thought from my essay How the Web Works:

"These problems are not really new to the web -- they are present just as much in print media too. For example, you only know how many magazines you've sold, not how many people have read them. In print media we have learnt to live with these issues, using the data which are available, and it would be better if we did on the web too, rather than making up spurious numbers."