The Mathematics of High Performance  Individual performance across a wide variety of fields is more a power law distribution than a normal distribution. [1]   This means that "ten percent of productivity comes from the top percentile, and 26% of output derives from the top 5% of workers," a more extreme ratio than the typical 80-20 rule in long-tail distributions.

The exceptions to this observation include "industries and organizations that rely on manual labor, have limited technology, and place strict standards for both minimum and maximum production" — essentially anywhere there's little opportunity to be exceptional.

The implication for entrepreneurial companies?  Laszlo Bock (Google SVP People Operations):  Managers at any company should ask, "How many people would you trade for your very best performer? If the number is more than five, you're probably underpaying your best person. And if it's more than ten, you're almost certainly underpaying."

[1] The Best and the Rest: Revisiting the Norm of Normality of Individual Performance; 2012; ERNEST O’BOYLE JR. (Longwood University) and HERMAN AGUINIS (Indiana University); Personnel Psychology, Vol. 65; pp79-119
Source: http://mypage.iu.edu/~haguinis/PPsych2012.pdf

[2] Inside Google's Policy to 'Pay Unfairly': Why 2 people in the same role can earn dramatically different amounts.  Richard Feloni; 11.Apr.2015; Business Insider UK;
Source: http://uk.businessinsider.com/google-policy-to-pay-unfairly-2015-4?r=US