The research firm believe that tracking a game's success via sales numbers is baloney. People like advertisers want to know how many people are playing (and talking about) their games, not how many people are buying them.
So they started tracking message boards, social networking sites and user content sites like YouTube to see which games were the most engaging, then compared that to the October NPD list of best-sellers.
The results are, as you'd expect, not the same.
LittleBigPlanet, for example, is much higher on NI's charts than it was on NPD's, courtesy of its heavy emphasis on community and user-generated content. GTAIV is back near the top too, courtesy of its multiplayer and, we guess, the fact it's still a talking point over six months after release.
Measuring the Social Report #3: Video Games [Networked Insights]