The stack rank is the _reason_ there's so much dead wood: managers have to keep mediocre performers on the payroll so that star performers don't get bad reviews and leave. You need star performance to get anything done, since Microsoft is not somehow exempt from the power-law distribution of programmer productivity. The accumulation of mediocre performers makes the organization "trust sparse" (the average employee is a low-net-value robot who exists only to absorb the bad reviews in place of the few who get stuff done), which seriously damages long-distance collaboration, since you can't tell in advance which employees are the bozos. The review system also creates a culture of extreme risk avoidance, as you can't trust the bozos you have on your team to actually code features properly, but you still have to give them work.