Measuring productivity is silly. Measure results.

Here's my desired review:

Entire team goes around and answers the question: who do you want to leave? Two strikes get another chance. Three strikes and they're gone.

Same with the boss.

Keep their job or replace em? More than three say replace the level up does a panel with the three.

During our last layoff the question for the managers was "if you could drop any headcount who would it be?"

We lost about 8% from that. Everyone I talked to said they were happy that the layoff got rid of the bad apples they knew.