Work expands to fill whatever time you've given it, however little there is to do

C. Northcote Parkinson noticed that Britain's Colonial Office kept adding staff throughout the 1930s even as the empire it administered was shrinking, and its Admiralty grew even as the navy's ships shrank in number. His explanation: bureaucracies generate work for each other regardless of the actual job left to do, and any task, given a week, will somehow take a week, however small the task really was. It's since become one of the most-quoted laws in management, despite starting life as a joke.

— C. Northcote Parkinson, Parkinson's Law — The Economist, 1955