Graphing a series of multiyear forecasts vs. actuals can provide insight into forecast accuracy and methods. This graph looks at a series of revenue per share projections for Apple
Note that none of the forecasts showed the exponential growth, but assumed essentially linear growth. (the forecast lines are gray and extend for multiple years. Actuals are blue line. The full analysis is by Horace Dediu at Asymco.com. A similar technique was used by the New York Times in analysis of federal budget forecasts.