The lesson is modest. Build for the person who exists, not the one in the model. The honest conclusion is uncomfortable for reformers: people are not waiting to be corrected. The point is not that people are foolish. The point is that reason is expensive, and we economise on it like everything else. In the studies we have, the effect is modest, reliable and almost entirely ignored by the people it describes.
The cost of being right
The remedy is rarely exhortation. It is a change to the situation so that the easier choice is also the better one. The point is not that people are foolish. The point is that reason is expensive, and we economise on it like everything else. Economists have spent decades modelling reason as a quantity. It behaves more like a weather system. If you want to see reason at work, watch a queue form where there is no reason for one.
The point is not that people are foolish. The point is that reason is expensive, and we economise on it like everything else. Understanding people turns out to be a more urgent task than changing them, and a great deal harder. Ask most people why they did what they did and they will give you a reason; ask them again a week later and the reason will have quietly changed. There is a version of this essay that ends with a policy prescription. This is not that version; the mechanism is interesting enough on its own.
