Worse, it's about the easiest statistic to manipulate, if you know that is going to be a Key Performance Indicator.

(Having said that, the mean is not difficult to manipulate)

There's an important game theory issue to KPIs:

- if everyone is behaving perfectly, then why bother checking the stat?

- if someone is behaving maliciously, and wants to game the stat, will they be forced to actually improve the situation?

A malicious actor barely has to break stride here.