A high performer can deliver 400% more productivity than the average performer.
Despite this, when most managers look at workforce statistics, all employees tend to be lumped together into a category so broadly defined that it becomes difficult to take meaningful decisions. If your average employee tenure is six years, is that good or bad? You could benchmark the Fortune 500 and find that indeed you would look pretty good, tied at 40th place. But if the people you are keeping are the low performers and your high performers are leaving, would that be really so great?