Refer to the input text as context and select the correct relationship between 'Janet Yellen' and 'economist' from the available options.
Options: location of formation, position held, manufacturer, 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