• by Jim Meskauskas , March 7, 2002

Looks like I've picked yet another topic that requires more than just one trip to the bar in order to quench one’s thirst.

There are a few opinions out there on the topic, but when pressed, I think everyone has some visceral belief that the amount of time one spends with a vehicle in a particular medium has an impact on the individual who is being engaged. Time, as well as Space, serves as the fabric of our reality. No reason why this can’t also be true for advertising.

It makes sense to us that more time spent with a thing means we are somehow being affected by that thing. This is why parents don’t want their children hanging out with the “wrong crowd,” walls in sanitariums are painted certain colors, and practice makes perfect.

But, even if we understand that time spent with a thing has some impact on us, why might this be important to advertising?

In traditional media we are forced to use certain surrogates to determine what and how our advertising might be working. We use demographics as surrogates for psychographics. We use lifts in awareness or purchase intent as surrogates for projected sales. We use vehicle exposure (to what extent a certain magazine or program might have a chance of being "seen" by an audience, for example) as a surrogate for advertising exposure.

In order to get the most complete picture of just what our advertising might be doing for us, however, one of the things that we all really want to get at is time spent with our ads. THIS is why session length is important as a metric for online advertising in ways that it CAN'T be for offline advertising. That's not to say it isn't important to offline advertising, but it's something that is impossible to determine in a readily meaningful way.

But that still doesn't answer why a session length metric might be important to online advertising. I've only barely explained that time spent with an ad can be important. What does session length lend to a determination of time spent with an ad?

Because session length can serve, for the time being, as a surrogate for time spent with an advertisement.

The difference between broadcast, let's say, and online, in this case specifically, is that in broadcast vehicle length doesn't have any correlate of message persistence. Basically, I can't have a "durable" message with the programming. I guess the closest thing would be those ghostly network IDs and logos that float in the bottom right-hand corners of one's television screen during programming. Online, the advertising can potentially live as long as the content, i.e. endure throughout the course of a visitor session.

This isn't to say that is how advertising works online, but for things like sponsorships, which provide the equivalent of signage at a sports stadium, the session length could prove a valuable metric for advertisers considering proposals of this sort.

I also think that if an online publisher wants to experiment with selling inventory based on "circulation" or unique visitors (that is the audience-based media currency I've written about, on and off, for the last year and a half) rather than on raw impressions, the session length metric might be useable as a way to differentiate the value of the impressions served rather than their frequency.

This may be a way to evaluating advertising on its own terms, but I'm not sure that advertising can be, in an evaluative sense, truly separate from the content within which it resides. I guess DR is something that, to a certain degree, serves as its own medium, where advertising is evaluated solely by its own rights. I think that in light of the sorts of tenuous connections we are still willing to draw between the advertising event and the brand engagement, reliance on the correlative aspects of advertising, such as the content in which we encounter it, will continue to be important to how advertising gets evaluated.

I haven't worked everything out, yet, about what a session-length valuation might look like, but it's a problem I'm interested in solving. And when I do, y'all will be the first to know.