Parkinson's Law is one of two observations made by the naval historian C. Northcote Parkinson in a 1955 satirical essay:
The essay starts by mentioning the first sense as a "commonplace observation", and the bulk of the essay discusses the second, which is what Parkinson winkingly dubs "Parkinson's Law". The first has been called the "personal version" of the law and the second, which is not stated explicitly, the "organizational version".
It is the first sense which is now most commonly called Parkinson's Law.
The essay is written as satire in response to the report of the Royal Commission on the Civil Service, which had been issued two days earlier. Despite its facetious origins, it has been widely adopted in management science and social psychology.
The first meaning â "Work expands to fill the available time" â has inspired various facetious corollaries, the best known being the Stock-Sanford corollary to Parkinson's law:
the Asimov corollary to Parkinson's law:
as well as corollaries relating to computers, such as:
The second sense was the main focus of the essay published in The Economist, and reprinted with other similar essays in the successful 1958 book Parkinson's Law: The Pursuit of Progress. The book was translated into many languages. It was highly popular in the Soviet Union and its sphere of influence. In 1986, Alessandro Natta complained about the swelling bureaucracy in Italy. Mikhail Gorbachev responded that "Parkinson's law works everywhere".
Parkinson derived the dictum from his extensive experience in the British Civil Service. He gave, as examples, the growth in the size of the British Admiralty and Colonial Office even though the numbers of, respectively, their ships and colonies were declining.
Much of the essay is dedicated to a summary of purportedly scientific observations supporting the law, such as the increase in the number of employees at the Colonial Office while the British Empire declined (he showed that it had its greatest number of staff when it was folded into the Foreign Office due to a lack of colonies to administer). He explained this growth using two forces: (1) "An official wants to multiply subordinates, not rivals", and (2) "Officials make work for each other." He noted that the number employed in a bureaucracy rose by 5âÂÂ7% per year "irrespective of any variation in the amount of work (if any) to be done".
Parkinson presented the growth as a mock-scientific mathematical equation describing the rate at which bureaucracies expand over time.
Observing that the promotion of employees necessitated the hiring of subordinates, and that the time used to answer minutes requires more work, Parkinson stated: "In any public administrative department not actually at war the staff increase may be expected to follow this formula" (for a given year):where:
In a different essay included in the book, Parkinson proposed a rule about the efficiency of administrative councils. He defined a "coefficient of inefficiency" with the number of members as the main determining variable. This is a semi-humorous attempt to define the size at which a committee or other decision-making body becomes completely inefficient.
In a chapter is devoted to the basic question of what he called comitology: how committees, government cabinets, and other such bodies are created and eventually grow irrelevant (or are initially designed as such). (The word comitology has recently been independently invented by the European Union for a different, non-humorous meaning.)
Empirical evidence is drawn from historical and contemporary government cabinets. Most often, the minimal size of a state's most powerful and prestigious body is five members. From English history, Parkinson notes a number of bodies that lost power as they grew:
A detailed mathematical expression is proposed by Parkinson for the coefficient of inefficiency, featuring many possible influences. In 2008, an attempt was made to empirically verify the proposed model. Parkinson's conjecture that membership exceeding a number "between 19.9 and 22.4" makes a committee manifestly inefficient seems well justified by the evidence proposed. Less certain is the optimal number of members, which must lie between three (a logical minimum) and 20. (Within a group of 20, factions or various individual discussions may occur, some of which may substitute for or displace the working of the whole committee, thus diluting the power of the leader, the chair of the committee proper.) That it may be eight seems arguable but is not supported by observation: no contemporary government (cabinet) in Parkinson's data set had eight members, and only king Charles I of England had a Committee of State of that size.