That is a good angle. Let me elaborate. I am not so much talking about the correctness of the metric, but about the certainty that you will get it, if your res

That is a good angle. Let me elaborate. I am not so much talking about the correctness of the metric, but about the certainty that you will get it, if your results are good. If there is no specific number someone can always say you performed bad one day before, for pretty much any reason (you did not care enough about the customer). This can destroy morale. Instead, if the metric is quantifiable and easy to check on a dashboard there is no way to deny it. By the time the evaluation comes there is no manipulation possible.