Since the early days of monitoring traffic on the web, one of the metrics that metering services provided for sites and agencies was session length.
Even the earliest PC Meter reports (the precursor to Media Metrix) had data points that indicated how much time a user spent, on average, with a particular site.
At first, no one was sure what to do with this information. To many, it was at best an interesting factoid. Then, for a brief moment, sites started including this tid-bit of data in their sales pitches. Site after site would come in and present, almost always including mention of the amount of time a user spent with their site. This was, I guess, done for a few reasons. Most notably, I think, it was to point out how loyal and dedicated an audience a particular website had. The more time the average user was on the site, the more committed a user they were. Some site sales organizations might have thought that average session length data might suggest an audience’s attention level. The greater the average time spent on the site, the more attention a user was paying to the content and, thus, an advertiser’s message. And perhaps others thought it would impress upon a media buyer the opportunity their client’s message would have to be seen by the site’s audience.
All of these have certain grades of validity, to be sure. Thinking back on it, gaming and game content sites were most fond of pointing out how much time the average user spent with their content. TEN, HappyPuppy, Heat.net… they all wanted to tell us how much more time than other sites their users spent with them.
I think this was initially done for lack of a better point of product differentiation. When you’ve got a thousand web sites out their all fighting over the same nickel, you’ve got to have SOMETHING unique.
The thing is, when all is said and done, no one has really ever figured out a way to do anything meaningful with session-length data and so it has gone by the wayside. It has become the parsley served with your restaurant-burger.
And so the session length data point languished as a forgotten honorable mention.
The question about session length data continues to be raised, however, usually by clients new to the Internet. And from time to time, I come across a site that will still mention it.
So why does it keep coming up and what might it mean?
Ultimately, I think that the real reason might have been something more sublime and intuitive than the reasons mentioned above.
Some have suggested that it is a useless metric that has little meaning; just ancillary data, really, to the more important data like uniques, impressions, reach, etc. Session length is a side dish, more like bread pudding than Beef Wellington.
I think that most of us all intuit that there might be something important about the amount of time an individual spends with a medium and the vehicles that define it.
I do not agree that session length is NOT a meaningful metric. I do agree that just what it means given the varieties and contexts of content is unclear, but to dismiss it out of hand because we are unsure of its implication isn't the best thing to do here.
There is no doubt that the amount of time spent with a medium has been an important factor in media planning over the years. Those of you with experience in traditional media may remember the "Media Quintile." This is a way of looking at a particular target or demographic's media usage based on TIME SPENT. A quintile is an even segmentation of a universe into 5 parts, each of those parts representing a "bucket" of media usage: Heavy, Medium-heavy, medium, medium-light, and light. These designations are based on time spent with a medium.
Now, as a subset of how much time is spent with a particular medium is how much time is spent with a specific vehicle within that medium. This is not easy to get with most traditional media (for broadcast, we assume program length as being a user's possible vehicle session length, and then Nielsen breaks that into 5 minute parcels), but if planners could, I think they would take session length into account when planning media.
With the Internet, we can get session length down to not only vehicle but also page. Whether or not this is meaningful to you depends on A) what the advertiser is trying to accomplish, B) what kind of media property your advertising runs on (dictated in no small part by the objective), and C) how the inventory is packaged and sold. Session length might mean nothing to a buy on Yahoo!, who really just sells massive amounts of impressions and has more of a "drive-by" audience. But this might be very important for a site selling fixed placements (sponsorships, surround sessions, "audience"-based inventory) like Salon.com, NYTimes.com, or some other vehicle used more for branding and awareness.
Though it isn't clear that session length should mean much to the pricing of inventory, it shouldn't be disregarded as not having impact on what a client's advertising can accomplish, especially if that advertising can be shaped to take advantage of that time spent with the medium and the vehicle.