zerosaurus on 15 February 2008
NPD is the usually the source for other gaming organizations because large amounts of money is pumped in their direction to spit out results for the video game industry to call accurate (or at least close to), the idea behind spending for their figures is they are accountable for gross negligent errors.
VGChartz on the other hand is NOT an industry driven stats collector but rather an amateur group (albeit a great amateur group) who have the understanding in statistical theory to throw out numbers that are on par with the so called-industry approved NPD.
