Lidor Wyssocky has posted a blog entry describing the problems associated with trying to measure the productivity of individual software developers as a result of introducing a new tool or process.
There has been much advice, research and debate over the years on the subject of measuring the productivity of software developers. Agile development methodologies rely heavily on the ability to react to change as indicated by certain metrics, some of which relate to developer productivity. However, in the spirit of Tom DeMarco's book Slack, Lidor suggests that it's a mistake to try and make every minute accountable:
Measuring people’s productivity as the percentage of time they spend on their primary task is relatively easy. But that doesn’t make it a meaningful measurement. People, and especially people doing creative tasks, might spend much of the time on other things beside their primary task. This is not necessarily a waste of time. On the contrary, it’s probably an essential ingredient of the creative process.