What is the relationship between Martin Winterkorn and Chief Executive Officer 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.

The crisis wiped about 20 billion euros ($22.4 billion) off VW’s market value this week, forcing Chief Executive Officer Martin Winterkorn to step down on Wednesday as the scandal widened and opened the door for the exit of other top executives.

Answer: position_held