In 1958, C Northcote Parkinson wrote a satirical book describing human behaviour, Parkinson's Law: The Pursuit of Progress. This was the source of the maxim Work expands to fill the time available. While initially a satirical work, it has been included into mainstream thinking. Indeed Parkinson's Law is so widely quoted that many do not realise it was intended initially as humour.
Simply put - work expands to fill the time available, but that is the headline. An example is given in the book of two people writing a postcard, an elderly retired person may take all day to do so, carefully choosing the card, thinking what to write and then walking to a post box. A busy person will pick the first card, write it and post it on the way home.
This is just the obvious example, many other examples were given by Parkinson. One of his most alarming one is in terms of civil servants. Most of the population assumes that a growing civil service reflects a growing workload. Parkinson says this is not so and uses the following argument:
Civil servant A is overworked (this may just be illusionary or as a result of reaching his level of incompetence1). He has only a few options; he may leave, share his work with colleagues at the same level or appoint two juniors. It is important to note that he has to appoint two juniors. A single subordinate would very quickly assume almost equal status with A in their own minds as well as others and would therefore be a rival. This is also the reason against sharing the work with someone on the same level. So now, assuming A didn't leave, we have A and two subordinates B and C. Very soon either B or C will complain about being overworked and two more subordinates to them will be appointed. Another two will have to be appointed to keep the other original subordinate happy.
Seven are now doing the work of one. All will be busy passing paperwork or these days e-mails between themselves, correcting each others grammar, passing decisions down the line then passing them up when they want someone else to take the blame. Person A is now reduced to management, something he may not be happy with, in fact he may have had his level of incompetence enforced on him.
Parkinson had a few variations on his idea. One being that in deciding on capital projects the time taken to reach a decision will be inversely proportional time to the cost of the scheme. For example, building a multi-million pound tent in London goes through on the nod, but deciding what shape the litter bins will be will invoke a month-long project. He theorises that when the costs go way beyond the incomes of those deciding they switch off, after all what's another million here or there. When the amounts are closer to those they are used to in their own lives they are more willing to debate over a few thousand.
Since Parkinson came up with his law it has been used in other situations. For example, Parkinson's Law of Data which states 'Data expands to fill the space available for storage'. Software seems always to be demanding more memory which in turn encourages more memory intensive routines to be evolved, this is of course closely linked to Moore's Law.
Other initially satirical laws of business have been written since, most recently The Dilbert Principle. Maybe in 20 years these too will be regarded not purely as a humorous read but as serious statements on how business was conducted at the time of writing.