What we do with it
- 01
Remember what people already told you. Asking for an address twice turns a two-minute task into five.
- 02
A visible end helps. “Three questions” gets finished faster than a form with no end in sight.
- 03
It applies to project plans as much as to forms.
Examples
Getting it wrong, getting it right.
Don't
A checkout that asks for the shipping address again on the billing step.
Do
“Same as shipping” already checked.
The evidence
What the research says.
Parkinson meant it as satire, and it has since been tested. In Judith Bryan and Edwin Locke's 1967 lab study, people given twice the time an addition task needed worked at a slower pace than people given just enough. They read it as a goal-setting effect: the time you're given acts as a target. Elliot Aronson and David Landy repeated it the same year with five minutes against fifteen, and people given fifteen spent more of it working on a five-minute task.
Sources
- Parkinson, C. N. (1955). Parkinson's law. The Economist, 19 November.
- Bryan, J. F., & Locke, E. A. (1967). Parkinson's law as a goal-setting phenomenon. Organizational Behavior and Human Performance, 2(3).
- Aronson, E., & Landy, D. (1967). Further steps beyond Parkinson's law: A replication and extension of the excess time effect. Journal of Experimental Social Psychology, 3(3).
Last reviewed November 7, 2026. How we keep this current