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

"Fed Chair Janet Yellen has been conspicuously silent, with no significant comments since July's congressional testimony,"wrote Standard Chartered senior economist Thomas Costerg in a note explaining the decision to switch from September to aDecember hike.

Answer: position_held