In order to understand the factors of forecasting, one should imagine himself as a part of a supply chain e.g. a factory. A factory 's job is to be able to supply the market demand with lowest operating costs possible. Forecasting in a factory plays the hardest role of knowing what to produce now in order to supply the demand in the future and containing the resources available on hand to do this. The challenge is not only to come up with the future demand and the efficient manufacturing design but also to beat the lead times in between the chains in the systems. The errors can be costly in this process. Overshooting in the forecasts will result in inventory costs in the factory, where underestimating will cause late orders, extra labor costs, missed sales opportunities, stockout costs, and even production close downs due to the lack of raw materials since not being ordered on time. Moreover, as the variety and the lifetime cycles of the products increase, (lifetime cycles actually decrease) the process becomes even more sophisticated since now you need to know the production queues and where to stop producing a certain type in addition to the challenge of knowing the right numbers to produce. And unfortunately one should note that in reality the only certain thing about a forecast is that it will be wrong and that 's why there will always be some costs. That is
References: Schroeder, G. R. Operations Management: Contemporary Concepts and Cases. McGraw-Hill, New York, NY. Fisher, L. M., Hammond, J. H., Obermeyer R. W., Raman A. Making Supply Meet Demand In An Uncertain World. Harvard Business Review, May-June 1994