Metrics change what we value. They even have an impact on our behavior.

So choosing a metric has effects. But it isn’t always clear what effect a metric will have beforehand. Maybe the short-term results are good, but in the long run it leads to bad habits. For a good example see Pick the right metric to incentivize the behavior you want.

So what is a good metric. From a technical point a good metric is comparative, understandable, a ratio or rate and the metric changes the way you behave (taken from Lean Analytics).

For always getting the “right” results, I haven’t found THE metric. Again Pick the right metric to incentivize the behavior you want gives a few tips on how to choose a good metric.