This is a great example of what happens when you try to incentivise intelligent people on very simple metrics.
This was well described in Freakonomics, and something Mr On Software bangs on about regularly. It's clear that there isn't really a good answer to the problem - actually that's not true. The answer to the problem is to have everyone working in a job they are happy in and proud of, one where they are intrinsically motivated, and give them enough information to allow them to make the correct calls when it comes to prioritising work. But I'm guessing that a large portion of the working world does not fall into this category.