Generally speaking, I am against setting strict rules in the workplace. But when I was a young manager, I had one unequivocal rule for everyone on my team: You cannot earn the highest rating on your performance review unless you have done something significant to improve yourself, learn a new skill, or otherwise do something to grow professionally. I kept the professional development part vague on purpose. I did not want to constrain my employees; I wanted to leave the “what” and “how” up to them.
This is not to say that someone who learned a valuable skill, but was an average performer, would earn a top rating. Not at all. An employee had to perform great and develop herself. My belief is that someone who earns a top rating does more than her job. A top performer performs great at her current role, while also continuously developing herself for the next role. And that is what I tried to communicate with this rule.