Work expands so as to fill the time available for its completion.

That sentence now belongs to productivity advice. It was published on 19 November 1955, in The Economist, as satire, by a naval historian, about the British civil service — and its author had no interest whatsoever in helping you clear your inbox.

Cyril Northcote Parkinson was writing after a Royal Commission report on the civil service, and his real subject is the essay's second and less-quoted claim: that bureaucracies grow at a steady rate regardless of the work to be done. Not because of the work. Independent of it.

His explanation has two parts, and both are unimprovable. An official wants to multiply subordinates, not rivals — because promotion depends on how many people report to you, and a peer is competition while a junior is credit. And officials make work for one another — two officials generate correspondence, review, approval and coordination that neither would have needed alone.

So the organisation grows by producing its own workload.

And then Parkinson did the thing that separates him from every other person who has ever made this joke. He supplied algebra:

x = (2kᵐ + P)/n

where x is new employees hired annually, k is staff seeking promotion by hiring subordinates, m is hours spent on internal memoranda, P is the span between hiring and retirement age, and n is administrative files completed.

It is a parody of a formula and it is also a formula, and the commitment is the point.

The famous first sentence is now used as advice: shorten the deadline and the work shrinks to fit. That works, and it is worth doing. But it is one operational corollary lifted out of a structural argument about institutions — and the structural argument is the part that explains why your organisation keeps hiring.