There are several methods for forecasting demand including opinion-based methods like surveys and experiments, time series analysis using trends and seasonal variations, and barometric forecasting using economic indicators. Time series analysis can involve graphical or statistical curve fitting to projected trends or exponential smoothing using actual observations and smoothing constants. Barometric forecasting uses indicator series that are coincident with or lead the demand being forecast through composite or diffusion indices.

4. Trend Projection Graphic Statistical Seasonal curve fitting curve fitting variation

5. Graphic curve fitting: the trend is projected graphically