Measure what you care about. If lines of code produced is your thing, then measure that. One year I decided to measure defects released into production, so I could find root causes. I discovered that bad code wasn't my biggest weakness; it was procedures for getting things into production, and procedures for testing and replicating the production environment. So I ended up spending more time getting that stuff right than I did before.

Different people have different kinds of responsibilities and things that should be important to them, based on what's going on in their business and with the rest of their team. Sometimes "hours spent writing code" is the thing for some people, but keep in mind it isn't always the formula for success for all people.