Predictions of how others will behave in a particular situation, made by persons with knowledge the situation. Rowe and Wright (2001) discuss principles for the use of expert opinions. Most important forecasts rely on unaided expert opinions. Research has led to many principles to improve forecasting with expert opinions. For example, forecasters should obtain independent forecasts from 5 to 20 experts (based on research findings by Ashton 1986; Hogarth 1978; and Libby and Blashfield 1978).