The GfK SE, established in 1934 as Gesellschaft für Konsumforschung (Society for Consumer Research) is Germany's largest market research institute, and the fourth largest market research organisation in the world, after Nielsen Company, Kantar Group and Ipsos. It was founded by an association of university teachers, among them Ludwig Erhard.
In May 2008 it acquired an equity stake in Deep-Packet Inspection company Qosmos in order to track and monitor Internet usage for marketing research.
In December 2011, GfK acquired Knowledge Networks, based in Palo Alto, California the United States, which does online research for consumer products and services, pharmaceuticals, retail, media, and public policy. KN's Dimestore platform offers unique platform for measuring the effectiveness of digital ad campaign with simple surveys of streaming video ads, that also allows real-time reporting.
In 2010, the company was the fourth-largest market research company by revenue.