The general approach is: performance, when measured, improves; performance, when measured and reported, improves exponentially. KPIs might be defined incorrect

The general approach is: performance, when measured, improves; performance, when measured and reported, improves exponentially. KPIs might be defined incorrectly, but their use is simple and straightforward for people to understand. This gives rise to Goodhart's Law, "when a measure becomes a target, it ceases to be a good measure." The best KPI is something that can't be gamed by those whose performance is being measured. This is probably impossible in practice.