Count on the best people outperforming the worst by about 10:1.
Count on the best performer being about 2.5 times better than the median performer.
Count on the half that are better-than-median performers outdoing the other half by more than 2:1.
What nearly everyone who has read that remembers is the following:
People with skill below 0.25 cannot meet the minimum requirements for the job, or cannot be productive enough to cover their labor costs. People with skill above 2.5 have likely been promoted beyond the parameters of that job.
Whenever someone exceeds base expectations to such an extent that they hit the ceiling for the position they are in, they either get recognized and promoted, they job-hop to the next rung up the ladder, or they throttle back their own performance to be proportional to their compensation.
There are a few jobs that are at the top of their respective career ladders, where there is no choice but to offer profit-sharing as a means of encouraging best performance. So you can get a 20x CEO, or a 50x celebrity performer, because they get paid a percentage, and there is nothing else to be promoted to, except young passive-investor retiree.
I don't have the book ready here, and it's been a long time since I last read it, but wasn't that the productivity for specific, limited and well-specified tasks? How about the productivity of tasks that only a subset of developers would be able to solve (which don't have to be that hard, like a bug-free binary search, which according to Bentley[1], eluded 90% of professional programmers)? How do you quantify the difference in performance for that?
In Peopleware, DeMarco and Lister write:
What nearly everyone who has read that remembers is the following: