The great thing about measuring developer productivity is that you can quickly identify the bad programmers. I want to tell you about the worst programmer I know, and why I fought to keep him in the team.
Once upon a time there was a lady in a taxi. It took such a long time for the lady to get to her destination in the taxi that she went to the town hall and told the man from the council. The man from the council wanted to figure out why the taxi journey was so slow, so he placed cameras at all the traffic lights in the town to measure how many cars went past, and how quickly. The traffic light cameras would click every time a car went past the lights.