Beware of metrics and targets.

This isn't an abstract problem. Targets can kill
The Observer, Sunday 22 March 2009

Excerpt:

"The Health Commission’s finding last week that pursuing targets to the detriment of patient care may have caused the deaths of 400 people at Stafford between 2005 and 2008 simply confirms what we already know. … [T]argets distort judgment, disenfranchise professionals and wreck morale. Put concretely, in services where lives are at stake – as in the NHS or child protection – targets kill. Targets make organisations stupid. Because they are a simplistic response to a complex issue, they have unintended and unwelcome consequences – often, as with MRSA [infectious disease picked up in hospitals] or Stafford [hospital], that something essential but unspecified doesn’t get done. So every target generates others to counter the perverse results of the first one. But then the system becomes unmanageable."

by Simon Caulkin

Follow Goodhart's Law:

When a measure becomes a target, it ceases to be a good measure.