Parkinson's Law

The law

Work expands to fill the time available for it.

A task given more time than it needs tends to take all of it. In interface design the law is used the other way round: when a product makes a task take less time, people finish sooner and feel the product respected their time.

Where it comes from

Cyril Northcote Parkinson, a British naval historian, introduced the law in a satirical essay in The Economist in November 1955 and expanded it in the book Parkinson's Law, and Other Studies in Administration in 1957. His target was bureaucracy: he observed that the British Admiralty's administrative staff kept growing while the number of ships and sailors fell, and argued that officials create work for each other regardless of how much real work exists.

The opening line about work filling the time available became the part everyone remembers. It is an observation about organizations, written as humour, not an experimental finding. Designers borrow it as a heuristic about time and attention.

What it means for an interface

• Set the pace for people. Shorter forms, sensible defaults and autofill let people finish faster than they would if left to fill every field themselves.
• Give realistic time estimates. "About 3 minutes" helps people budget attention. An open-ended task with no estimate invites drifting and abandonment.
• Keep sessions short and complete. Break long tasks into parts that can be finished in one sitting, with progress saved between them.
• Do not create time pressure for its own sake. A deadline helps when it is real, such as a reservation hold. A fake countdown is a dark pattern.

Examples

Checkout autofill. A checkout that fills the address and payment details from the browser can be completed in seconds. The same form filled by hand takes minutes, and every extra minute is a chance to leave.

Survey estimates. A survey that states its length up front, and keeps to it, is completed more often than one that does not say how long it is.

Meeting tools. Calendar tools that default to 25 or 50 minutes instead of 30 or 60 use the law: the meeting fills the shorter slot and leaves time between meetings.

Where it is misapplied

• Fake urgency. Countdown timers that reset, or "only 2 left" when it is not true, use time pressure to rush people into decisions.
• Treating it as research. It is a satirical observation about bureaucracy. Do not cite it as evidence that a task will take a given amount of time.
• Rushing considered decisions. Some choices, such as health plans or contracts, deserve time. Speeding them up does not serve the person.
• Cutting time from the wrong place. Removing a confirmation step to save seconds can cost far more time when an error follows.

Checklist

• Every form field has been checked for autofill, a default or removal.
• Longer tasks state an honest time estimate up front.
• Long tasks can be paused and resumed without losing work.
• No timer or scarcity message is shown unless it reflects a real limit.
• Steps that protect people from costly mistakes are kept even when they add time.

Related

• Goal-Gradient Effect: a near, visible goal keeps effort focused.
• The Doherty Threshold: fast responses keep people in the flow of a task.
• Tesler's Law: the product can absorb work so people spend less time on it.