A mechanism to optimally balance cost and quality of labeling tasks outsourced to strategic agents.

We consider an expert-sourcing problem where the owner of a task benefits from high quality opinions provided by experts. Execution of the task at an assured quality level in a cost effective manner becomes a mechanism design problem when the individual qualities are private information of the experts. The considered class of task execution problems falls into the category of interdependent values, where one cannot simultaneously achieve truthfulness and efficiency in the unrestricted setting due to an impossibility result. We propose a novel mechanism QUEST, that exploits the structure of our special class of problems and guarantees allocative efficiency, ex-post incentive compatibility, and strict budget balance. Our mechanism satisfies ex-post individual rationality for the experts and we also derive the weakest sufficient condition under which it is ex-post individual rationality for the center as well.