Who said Every person reaches to his level of incompetence?

The phrase "Every person reaches the level of their incompetence" is associated with the Peter Principle, which was formulated by Dr. Laurence J. Peter in his 1969 book, "The Peter Principle: Why Things Always Go Wrong." The principle suggests that in a hierarchy, people tend to be promoted until they reach a position where they are no longer competent. This concept highlights the limitations of promotion based solely on performance in previous roles.