The Peter Principle is the principle that “In a Hierarchy Every Employee Tends to Rise to His Level of Incompetence.” It was formulated by Dr. Laurence J. Peter and Raymond Hull in their 1969 book The Peter Principle. Whether intentionally or inevitably, every person who is doing a great job will be promoted until they no longer have that job. The promotion is not necessarily to a more difficult job, but it is not the job the person was trained to do. For example, a management position is a different skill set than how a programmer has proven themselves.

via Errata Security: Peter Principle.