Wow; I guess if you are doing product development, everything is so clear cut! But what if you are a researcher? Your primary output is creative, so measuring the amount of code or text you write is not very effective. I don't think just researchers have this problem, but anyone who has to do any substantial amount of real thinking or design, even most programmers have to think a bit about what they need to write. And sometimes you need to twist your brain to do it.