Measuring developer productivity is a difficult challenge.
Conventional metrics focused on development cycle time and throughput are
limited, and there aren’t obvious answers for where else to turn.
Qualitative metrics offer a powerful way to measure and understand
developer productivity using data derived from developers themselves.
Abi Noda and Tim Cochran begin their
discussion by explaining what a qualitative metric is and
why we shouldn’t reject them for being subjective or unreliable.
Source: martinfowler