> Uh, I'm pretty sure the best employees in any field are worth 10x what the worst employees are, whether you're writing code, assembling a car or gutting fish.

I've worked at FedEx as a package handler before. That is absolutely not the case there. The absolutely best employees might be 3x more productive than someone who's mediocre with 2 weeks of experience. When the job is picking up boxes off of a conveyor belt and putting them in trucks, your walking speed is one of the key limiters. And no one can walk 10x faster than someone else. Not for a 6-8 hr shift.

Some jobs - especially jobs that involve heavy manual labor - just don't have a wide range between the most and least productive employees.