C. Northcote Parkinson's rule that in a bureaucracy work expands to fill the available time

Parkinson's law is the adage that "work expands so as to fill the time available for its completion". It is sometimes applied to the growth of bureaucracy in an organization. This law is likely derived from ideal gas law, whereby a gas expands to fit the volume allotted.

Articles

Bureaucracy and the Civil Service in the United States, by Murray Rothbard, The Journal of Libertarian Studies, 1995
Historical account of the evolution of the United States Civil Service and attempts to reform it, from its beginnings through the early 20th century
"The continuing rise in the total of government employees 'would be much the same whether the volume of the work were to increase, diminish, or even disappear.' Parkinson identifies two 'axiomatic' underlying forces responsible for this growth: (1) 'An official wants to multiply subordinates, not rivals'; and (2) 'Officials make work for each other.'"
The Snare of Government Subsidies, by Gary North, Mises Daily, 31 Aug 2006
Explains how government starts by granting a benefit to some group (purportedly for the public interest), someone takes advantage of the system, the group is asked to police itself, cheating grows, a crisis is perceived, leading to increased interventions
"Once the grant has been made, the beneficiaries use it for their purposes. The money is spent. Parkinson's Law takes over: expenditures rise so as to equal income. But expenditures are always difficult to reduce, especially in large, bureaucratic organizations. The firms become used to the higher income. The income becomes part of annual forecasts. Managers expect it to continue."

Books

Parkinson's Law
    by C. Northcote Parkinson, 1957

The introductory paragraph uses material from the Wikipedia article "Parkinson's law" as of 30 Jun 2018, which is released under the Creative Commons Attribution-Share-Alike License 3.0.