Energy needs...oil supplies...inflation rates...the demand for new homes...in concerns like these, forecasting plays a crucial role. Forecasts not only determine how billions of dollars will be spent by also commit national policies far into the future; yet, no one really knows how to judge the reliability of forecasts. In this innovative study, William Ascher examines the records of expert forecasting of national trends in population, economics, energy, transportation, and technology over a fifty-year period. The results help to identify both the accuracies and hidden biases of forecasting techniques, information that should be of vital interest to all policy-makers and planners.