I agree with Gilb's law, and I measure a number of things on projects I lead. However, there is a difference between measuring things that are indirect and imprecise and measuring productivity.
So I disagree that productivity can be measured, but agree that there are things you can measure and agree that measuring those things is valuable.
In the quoted example, Joel's eigth test measures the environment for interruptions. This is a good thing to measure. However, this is not the same thing as measuring productivity, because then we jump to the conclusion that "Working alone in an office with a door is more productive than pair programming because pairs interrupt each other constantly."
So, my thesis is that you can and should measure lots of things, but if you are not directly measuring productivity it is misleading to pretend that you are.
So I disagree that productivity can be measured, but agree that there are things you can measure and agree that measuring those things is valuable.
In the quoted example, Joel's eigth test measures the environment for interruptions. This is a good thing to measure. However, this is not the same thing as measuring productivity, because then we jump to the conclusion that "Working alone in an office with a door is more productive than pair programming because pairs interrupt each other constantly."
So, my thesis is that you can and should measure lots of things, but if you are not directly measuring productivity it is misleading to pretend that you are.