The evidence here is thinner than the confident commentary suggests, and the honest position is a shrug with a direction of travel. The point is not that people are foolish. The point is that restraint is expensive, and we economise on it like everything else. 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. The lesson is modest. Build for the person who exists, not the one in the model.
Where it overreaches
The point is not that people are foolish. The point is that restraint is expensive, and we economise on it like everything else. We describe the departure from the model as an error. We might equally describe the model as a hopeful guess about us. It is tempting to call this irrational. It is more useful to ask what it is for. The mind that evolved for small groups and immediate dangers is now asked to manage a pension. It does its best.
