Work performance refers as much to the “doing” of the job as to the “result.” Even so, as the workforces of many industrialized countries grow older, concerns about the relationship between age, work performance, and productivity have become more prominent. Many factors fuel these concerns, including persistent negative stereotypes of older workers (Posthuma and Campion, 2009), a paucity of studies with data and designs capable of producing convincing evidence, and fundamental methodological differences in how to best measure work performance (Hardy, 2006). Narrowly defined, work performance is equated with individual productivity; more broadly conceived, it denotes how well workers master the requisite skills, complete tasks, execute instructions, interact with colleagues, and contribute to the success of the enterprise (Skirbekk, 2008). Work performance relies on a combination of “soft” (reliability, accuracy, commitment, sociability) and “hard” (technological expertise, mental and physical capacity, flexibility) skills and has an important collective dimension, which complicates the process of making individual-level assessments. Employers recently have been adopting competency-based work performance reviews designed to capture the quantity and quality of the work performed; however, negative stereotypes can bias any assessment (Finkelstein, Burke, and Raju, 1995).