Utilize the input text as a context reference, choose the right relationship between 'Janet Yellen' and 'economist' from the options.
Options: manufacturer, position held, location of formation, operator

"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.
position held