Well Bell Curve is also called Forced Distribution.
This is one of the few Methods of Performance Management.
Its is a Comparative Performance Management System.
Employees' ratings are forced to keep in a specific trend that look like a Bell.
For example:
It is considered that: Excellent Employees in a Department should be not more than 10%, Good 20%, Satisfactory 40%, Marginal 20% and Unsatisfactory 10%.
Thus, all employees in a department are rated keeping this trend in mind.
Once all employees are rated in this way, the polonomial trend in the Graph looks like a BELL CURVE.
Issue:
The employees are not as satisfied with such sort of Comparative Analysis.
In their view, this is not a justified way as their supervisor is not free to rate on the basis of Performance rather he has to compare among the performances.
...
Hope the above will be helpful for your quest.
Once you understand this, Kindly confirm. :)