Behaviors of the Blogosphere II
Rick Buner, who was its project manager, offers some explanation of the methodology behind comScore’s controversial blog advertising survey.
One funny thing to me is that within the bubble I live — Internet advertising and media research — no one argues much anymore over the methodology of comScore and their chief rival Nielsen//NetRatings, in part because we’ve heard the explanations before but also because they’re such household names in our sector we don’t think to worry about it much. All the biggest web sites and online ad agencies and advertisers are quite familiar with comScore and their numbers. But apparently in the blogosphere they’re not so familiar.
[O]ne key question is do they count “unique visitors” by IP addresses, cookies or some other means? Probably IP addresses, which is the most common. At least this package distinguishes “visits” from “visitors,” as many don’t and bloggers often get confused thinking “visits” (which is surfing sessions) is the same as visitors (unique people), as visitors can have multiple visits during a month.
comScore’s panel used for this study comprises only U.S. residents. For advertiser purposes, that’s what most advertisers care about. Also, because of it’s very construct, it would be nearly impossible to get 100% international panel coverage (e.g., Iraq, Nigeria, Belize, etc.).
So their numbers exclude traffic from international sites. (The Methodology section of the report says the sample is U.S. only, but it doesn’t dwell on the point.) Many U.S. sites may between 10-50% traffic from international visitors. That may also explain a lot of the variance.
The unredacted post explains in much greater detail. The bottom line is that comScore is measuring something much different than, say, SiteMeter. Further, as any of us with SiteMeter, our own host-provided stats packages, and BlogAds can attest, different packages vary wildly in their calculations.
Still, if Henry Copeland started using comScore’s metric package over at BlogAds, I wouldn’t complain.