I was half of a very productive duo on a greenfield project subsystem - a project I joined midway: my partner wrote a lot of code, I estimate ~70% of final lines in the code base were his. What the LoC count won't tell you is all the refactoring, deletion, tests and error handling code I had to add, because his code only worked for the happy path. Can you say he was being 2x more productive than I was? I say no, because he was breaking the nightly build at least once a week before I joined, blocking the rest of the team, this ended when I added pre-commit tests.
