This chart applies to every profession, but it is most pronounced in technical, teaching, medical, law enforcement, sales, recruitment, management, among others:
This chart is supported by numerous studies.
Can productivity be negative ? Sure.
Clients leave, good employees get demotivated and quit, or any of these bad things happen:
An excellent policeman will solve a crime, while a bad one will charge an innocent person. An excellent developer will produce a huge system, while a poor performer will bring it down.
Once in a thousand years bad employees can make a tourist attraction for you such as this Tower of Pisa:
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The point of the chart at the top of the article is that we are better off with good employees. Higher compensations are offset by orders of magnitude better output.