From what I've seen from working on two projects with more than 100 engineers is that they break down into these categories:
20% - Not productive. They can't get their tasks done, and after awhile, no one even expects them to. They get routed around.
65% - Neutral. The quality problems and technical debt they incur matches their productive work.
12% - Net negative. They introduce hard to fix bugs and technical debt beyond their productivity.
3% - Gods. They do almost all the productive work. Without these types of people, no large project would ever get done.
20% - Not productive. They can't get their tasks done, and after awhile, no one even expects them to. They get routed around. 65% - Neutral. The quality problems and technical debt they incur matches their productive work. 12% - Net negative. They introduce hard to fix bugs and technical debt beyond their productivity. 3% - Gods. They do almost all the productive work. Without these types of people, no large project would ever get done.