a social science principle that states that when a metric is used as a target or indicator of performance, it tends to lose its validity and distort the system it is supposed to measure. This is because people will try to manipulate or game the metric to achieve the desired outcome, rather than improving the underlying process or quality

Or, more important a metric, more likely it will be manipulated

given by Donald T. Campbell, a Psychologist and social scientist wrote about Introduction to Research Methodologies