Best efforts are essential. Unfortunately, best efforts, people charging this way and that way without guidance of principles, can do a lot of damage.
The merit rating nourishes short-term performance, annihilates long-term planning, builds fear, demolishes teamwork, [and] nourishes rivalry and politics. It leaves people bitter, crushed, bruised, battered, desolate, despondent, dejected, feeling inferior, some even depressed, unfit for work for weeks after receipt of rating, unable to comprehend why they are inferior. It is unfair, as it ascribes to the people in a group differences that may be caused totally by the system that they work in.
Management of a system requires knowledge of the interrelationships between all of the components within the system and of everybody that works in it.