I'm more interested in why employees don't band together to game the system and ensure a given outcome, then split the winnings. Like a sort of a pyramid scheme - you and a buddy agree that this quarter it will be you who gets promoted and split the bonus/raise with your buddy. Then you get a third buddy and get him in on it if he agrees to let the second buddy be promoted this quarter. Now you're splitting 3 raises among 2 people. Then you get a fourth buddy in and promote the third one and so on. The system ends once the group has too many people at a high position. At that point any new employee joining the company at a low position is screwed, probably. Also at this point infighting will probably break out from people who don't want to split their raises with the ones with less money, given that they don't have a way of advancing any further. Obviously the only way to win at this is to be the very first person who, after everybody leaves, gets left with the highest position and highest salary. Which is why I called it a pyramid scheme.
How visible and gameable are the metrics, though? You'd have to ensure your metrics were better than some, worse than others, but NOT so much worse as to be dangerous.
Also, that sounds like a horrible amount of concerns for a developer. I'd like to build and ship code, not worry about measuring performance.
