What Is It For?

What is the purpose of the annual performance review? This is from the Harvard Business School's blog Working Knowledge for Business Leaders.
Perhaps a more important issue is the objective of the review itself. Is it to weed out poor performers? To recognize the so-called A players? To provide the basis for compensation decisions? To provide clues to future opportunity within the organization? To map out an individual plan for personal development? All of these? Too often this is unclear. Is it any wonder then that managers, many of whom receive little or no training in how to do it, conduct the task of reviewing performance so poorly?
Too many companies pay lip service to the performance review. Managers avoid conducting the review because it's distasteful. Many times employees don't know the purpose of the review. Managers don't have time to properly council the employee throughout the year to improve performance.