Utilize the input text as a context reference, choose the right relationship between Glencore and Ivan Glasenberg from the options. Options: 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.

Glencore boss Ivan Glasenberg remains an undisputed billionaire, but the value of his stake has dropped by some 70 per cent.

Answer: chief_executive_officer