Utilize the input text as a context reference, choose the right relationship between Janet Yellen and president 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.

Even with some key figures such as the Fed chair Janet Yellen and ECB president Mario Draghi missing, any headlines from a central bank meeting in Jackson Hole will be high on the agenda on Friday.

Answer: position_held