Peter and Hull refer to this as the “level of incompetence” and suggest that many jobs tend “to be occupied by an employee who is incompetent to carry out their duties.” The core idea was that workers continue to get promoted, so long as they produce effectively, but at some point they get promoted one too many times and are unable to remain efficient. In their 1969 book The Peter Principle, Laurence Peter and Raymond Hull dissected the relationship between promotions and competence in the workplace.
