Affective forecasters often rely on memories of past events. When people report memories for past events they may leave out important details, change things that occurred, and even add things that have not happened. This suggests the mind constructs memories based on what actually happened, and other factors including the person's knowledge, experiences, and existing schemas. Using highly available, but unrepresentative past memories, increases the impact bias. Baseball fans, for example, tend to use the best game they can remember as the basis for their affective forecast of the game they are about to see. Commuters are similarly likely to base their forecasts of how unpleasant it would feel to miss a train on their memory of the worst time they missed the train Various studies indicate that retroactive assessments of past experiences are prone to various errors, such as duration neglect or "decay bias". People tend to overemphasize the peaks and ends of their experiences when assessing them (peak/end bias), instead of analyzing the event as a whole. For example, in recalling painful experiences, people place greater emphasis on the most discomforting moments as well as the end of the event, as opposed to taking into account the overall duration. Retroactive reports often conflict with present-moment reports of events, further pointing to contradictions between the actual emotions experienced during an event and the memory of them. In addition to producing errors in forecasts about the future, this discrepancy has incited economists to redefine different types of utility and happiness (see section on economics).