"The Peter Principle" first appeared as an article in Esquire magazine in January 1967; two years later, Laurence J. Peter and Raymond Hull turned the material into a best-selling book.
The most memorable tenet -- "in a hierarchy, every employee tends to rise to his level of incompetence" -- was supplemented by Peter's Corollary ("in time, every post tends to be occupied by an employee who is incompetent to carry out its duties") and, lastly, "Work is accomplished by those employees who have not yet reached their level of incompetence."
* "The Peter Principle: Why Things Always Go Wrong" (1969 book): @
* "How the Peter Principle Works" (money.howstuffworks.com): @
* Peter obituary (New York Times, January 1990): @
* "Laurence Peter" (The Economist, January 2009): @