The other problem is that in a 100,000 person company there are many nuanced roles and where one person fails or struggles in one context, they may well excel i

The other problem is that in a 100,000 person company there are many nuanced roles and where one person fails or struggles in one context, they may well excel in ten others. It's a lot harder to accurately measure overall performance when the manager is biased and the employee may well have been strong-armed or pigeonholed into their current position.