Performance Appraisal Method - "Forced Distribution"
Forced distribution is a form of comparative evaluation in which an evaluator rates subordinates according to a specified distribution. Unlike ranking methods, forced distribution is frequently applied to several rather than only one component of job performance.
Use of the forced distribution method is demonstrated by a manager who is told that he or she must rate subordinates according to the following distribution: 10 percent low; 20 percent below average; 40 percent average; 20 percent above average; and 10 percent high. In a group of 20 employees, two would have to be placed in the low category, four in the below-average category, eight in the average, four above average, and two would be placed in the highest category. The proportions of forced distribution can vary. For example, a supervisor could be required to place employees into top, middle, and bottom thirds of a distribution.
Forced distribution is primarily used to eliminate rating errors such as leniency and central tendency, but the method itself can cause rating errors because it forces discriminations between employees even where job performance is quite similar. For example, even if all employees in a unit are doing a good job, the forced distribution approach dictates that a certain number be placed at the bottom of a graded continuum. For this reason, raters and ratees do not readily accept this method, especially in small groups or when group members are all of high ability.