[nradov]

The smallest organizational unit at which productivity can usefully be measured is an agile team of about 7 people. Below that size the effort of quantifying productivity exceeds any possible value of doing so, and incentivizes the wrong behaviors.

A good manager can get a reasonable subjective sense of individual productivity but won't be able to quantitatively measure it.

[mundo]

I agree, and I would add that there is one good subjective way to measure the productivity of individual developers, and that is talking to their teammates.