The Peter Principle (developed by Laurence J Peter and published
by William Morrow and Company in 1969) says that people in any hierarchy tend
to rise to their “level of incompetence”, because the skills required to make
someone good in one job, are not necessarily the skills required for another
job. For example, a good engineer would probably be a bad manager, and a good
manager would probably be a bad engineer.
I had never heard the name “The Peter Principle” but very
quickly after starting work in 1980, I heard a saying: “People tend to be
promoted to their level of incompetence”. Very soon afterwards (and throughout
a professional career spanning 40 years) I have seen it happen with my own
In 2018, professors Alan Benson, Danielle Li, and Kelly Shue
analyzed sales workers' performance and promotion practices at 214 American
businesses to test the veracity of the Peter principle. They found that these
companies tended to promote employees to management position based on their performance
in their previous position, rather than based on managerial potential.
Consistent with the Peter principle, the researchers found that high performing
sales employees were likelier to be promoted, and that they were likelier to
perform poorly as managers, leading to considerable costs to the businesses.
 - Benson, Alan; Li, Danielle; Shue, Kelly (February 2018). "Promotions
and the Peter Principle". NBER
Working Paper. 24343: 1–54. doi:10.3386/w24343.
Retrieved May 22, 2018.