The Westport, Connecticut-based Greenfield had revenues of $13.5m (拢9.2m) for the year to December 31. It will become part of Kantar's Millward Brown operation.
In a statement, WPP said: "The acquisition will provide Millward Brown's clients with the most comprehensive, integrated qualitative and quantitative offer in North America and further strengthens The Kantar Group's position in the information and consulting industry worldwide."
Founded in 1983, Greenfield Consulting is one of the US's leading qualitative research firms and works with marketers globally across a broad range of consumer marketing issues, including branding, advertising, new product development and online marketing-related research.
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