It's a general thing about data. Just because it is easy to measure doesn't mean its a useful metric. My hunch is that as expertise increases for developers,

It's a general thing about data. Just because it is easy to measure doesn't mean its a useful metric. My hunch is that as expertise increases for developers, LOC/day initially goes up, as they have to think less about language constructs and how to do certain things. Once a certain level of expertise is reached, LOC/day goes down, as the developer figures out how to do more with less code and spends more time in decision making and planning.