Explain how a misspecified benchmark distorts attribution and appraisal analysis

If the benchmark does not reflect the manager's style, the gap between them shows up as apparent skill or failure. A small-cap value manager measured against a large-cap index is credited in a year when small value stocks rally and blamed when they lag, although neither result reflects decisions the manager made. In attribution, style differences surface as spurious allocation or selection effects; in appraisal, alpha, the information ratio and the appraisal ratio are biased, and a portfolio beta far from the benchmark's distorts risk adjustment. The consequences are practical: a skilled manager may be fired, an unskilled one retained, or active fees paid for beta. The remedy is a benchmark that passes the quality tests, such as a style or custom index.