They're wrong more often than right and just retroactively adjust their bogus numbers once MC, Chart Track and NPD come out. Its fiction, and not even believable fiction.
Just to clarify:
GfK Group:
* Market research institute based in Germany, world's 4th largest market research organisation (1.5 billion annual revenue)
* Tracks the entirety of European video game sales, as:
GfK Chart-Track - Acquired subsidiary, tracks U.K., Ireland video game sales
GfK Retail and Technology - Massive international network tracks video game sales from: Austria, Belgium, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Italy, Latvia, Lithuania, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, and Ukraine, among other countries around the world
GfK is a close partner of the NPD Group and they work together in many instances.
* Sony, Microsoft, and Nintendo all believe GfK data as fact, and use it when determining future corporate strategy. Nintendo also uses its own proprietary services.
* GfK data is used by leading video game publishers like Ubisoft, Activision, EA, and Take-Two to track the European sales of their video games.
NPD Group:
* International research institute based in New York
* Leading authority for North American and Australian sell-through data
* Tracks the following video game sales:
NPD Group - USA
NPD Group - Canada
NPD Group - Australia (partnered with GfK)
NPD Group - New Zealand (partnered with GfK)
* Sony, Microsoft, and Nintendo all believe NPD data is fact, and use it when determining future corporate strategy
* NPD data is used by leading video game publishers like Ubisoft, Activision, EA, and Take-Two to track the North American sales of their video games.