What are the realistic demand planning method?

The techniques for Demand Planning for procurement vary from industry to industry. However, the following must be kept in view while engaging in such an exercise:

• One Rule may not be applicable and hold good in all cases.
• Always incorporate a reasonable degree of uncertainty
• Be prepared for the unexpected
• The model must be simple and not too complicated to comprehend

There are quite a few. Most people use statistical forecasting tools once they have smoothed the history i.e no spikes or dips. Then it also depends on the product, is it a seasonal product or a trend (growing) product.