What is the relationship between GfK and Market research in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

Market research company GfK (Swiss: GFK.SW - news ) said its monthly sentiment index jumped to +7 in August from +4 in July, matching June's figure, which was the highest since January 2000.

Answer: industry