Put a number on luck and it becomes a target; put a target on it and the number stops meaning what it meant. None of this is new. Adam Smith noticed most of it, and then the profession spent two centuries forgetting. Notice how rarely anyone is argued out of the second helping, and how often they are simply moved past it by a change in circumstance. We describe the departure from the model as an error. We might equally describe the model as a hopeful guess about us.
What the evidence shows
The strange thing about the second helping is not that it exists but that it works, most of the time, for most people. In the studies we have, the effect is modest, reliable and almost entirely ignored by the people it describes. Put a number on luck and it becomes a target; put a target on it and the number stops meaning what it meant. The lesson is modest. Build for the person who exists, not the one in the model.
