Fiedler's forecasting rules:

1. Forecasting is very difficult, especially if it's about the future.
2. For this reason: He who lives by the crystal ball soon learn to eat ground glass.
3. Similarly: The moment you forecast you know you're going to be wrong, you just don't know when and in which direction.
4. Nevertheless, always be precise in your forecasts because: Economists state their GNP growth projections to the nearest tenth of a percentage point to prove they have a sense of humor.
5. Another basic law: If the facts don't conform to the theory, they must be disposed of.
6. If you've always had doubts about the judgments of forecasters, it's quite understandable because: An economist is a  man who would marry Farrah Fawcett-Majors for her money.
7. By the same reasoning, your suspicions about the narrow range of most forecasts are justified: The herd instinct among forecasters make sheep look like independent thinkers.
8. When presenting a forecast: Give them a number or give them a date, but never both.