NONE: RE: ONLINE-ADS>> Really basic question about counting 'unique

RE: ONLINE-ADS>> Really basic question about counting 'unique

Steve Podradchik (
Tue, 13 May 1997 19:09:10 -0700

Precedence: bulk wrote:

>Most of the stuff in this list is over my head. I'm just getting my feet wet
>in the advertising thing and I have a question about the counting of 'unique
>impressions per time period', which if I'm not mistaken is the standard way
>of charging for ads.

Actually the most common method is, I believe, to just pay for a # of
impressions not 'unique' impressions for the reasons you list below.

>The question: If 'uniqeness' is determined by the IP address of the document
>requester, how does one take into account dynamic assignment? That is, most
>ISPs assign a dialup customer any one of a number of IP addresses each time
>they dial up. So hits on a page from several different IP addresses actually
>represent the same person requesting the page during an unknown number of
>distinct sessions.

The best way to tell is by using a cookie that uniquely identifies each
visitor. That is, the first time you visit a site (or page or see a
specific ad), the web server or ad banner server can issue you a unique ID
-- a 'cookie'. The server can ask for it later and use this to determine
if you've seen the page/ad/whatever before. Of course since most web sites
do not use such cookies, this doesn't apply.

Moreover, even a cookie system isn't perfect because it can become confused
if more than one person use one computer or one person uses multiple web
browsers or manually clears his cookies or (heaven-forbid) rejects cookies.
Better than just using an IP but not perfect.

Finally, due to web browser caching, let alone proxy servers and the like,
it's essentially impossible to really know how many times an ad has
actually been seen. You can know the 'minimum' # based on how many times
the ad was sent to the user but each person may have actually seen the ad
several times due to the wonders of the Back button. Or they may have
never really seen it at all because it was delivered by some Push system
while the user was at lunch. It's not really different than Print -- you
know how many magazines were distributed (more or less) but you can only
estimate the # of people who actually read it. Computers are merely
digital, not perfect.

Steve Podradchik
Marketwave (makers of the Hit List family of log analysis products --
10,000 users and growing)

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