[pjc50]

Star performers are not inherently more productive - context is important. They are talented but also benefit from the system supporting them. In one study, the performance of 10x Wall Street analysts crumbled when they switched employers if their team did not come with them.

http://en.wikipedia.org/wiki/Alexey_Stakhanov

Stakhanov was held up as the >10x more productive coal miner; however, it's now generally understood that this was the result of a propaganda effort, and he had a team preparing and clearing for him.

This is a common risk in work-rate-measuring systems, how do you account for worker A spending time which saves the time of worker B? Especially in knowledge work, where the old guy/gal who does very little but carries all the oral history of the company in their head can be more important than anyone realises.