Institutions know all this, of course, which is why the late fee is so rarely left to chance. Consider the late fee. It is a small thing, and small things are where habits live. Notice how rarely anyone is argued out of the late fee, and how often they are simply moved past it by a change in circumstance. The measure that matters is not what people say about patience but what they do when nobody is scoring.
Who should read it
The lesson is modest. Build for the person who exists, not the one in the model. Put a number on patience and it becomes a target; put a target on it and the number stops meaning what it meant. The textbook treats patience as a preference to be revealed. In practice it is a story we tell ourselves after the fact. Economists have spent decades modelling patience as a quantity. It behaves more like a weather system.
