All large companies have to accept that they will lose some great people and keep some bad people. If a company decided to perform an evaluation at a random poi

All large companies have to accept that they will lose some great people and keep some bad people. If a company decided to perform an evaluation at a random point in time, I doubt stack ranking would, on average, perform much worse than any other technique. The problem with stack ranking is the dynamics it encourages. Any set of rules is going to be gamed, so a goal for an HR policy should be to ensure that the dynamics created while gaming the system are beneficial to the company. The real damage of stack ranking happens in between ranking periods.