The fastest developers are those who barely put in bugs in the first place not those who are good at finding the bugs they themselves put in.
Example: Two developers writes half of a project. Developer A's code has 10 bugs, developer B's code has 1 bug. They both work together to fix the bugs, developer A fixed 4 of A's bugs while B fixed 6 of A's bug and his own bug. In total A fixed 4 and B fixed 7. In this case it looks like B was almost twice as effective, but if B didn't have to fix A's bugs he would have been way faster, especially since fixing others bugs is way harder than fixing your own.
