Forecasting could be over a long range with time span of years or could be over a short time frame such as weeks or even days. Errors in forecasting tend to be larger as the planning period gets longer. Uncertain factors that influence the demand may not be well estimated over a long period of time. There are many forecasting methods based on information available and market variations There is no golden rule or model that fits all circumstances. A good forecasting method should minimize the error between the actual demand and forecasted value. We will study some of the forecasting methods in the following pages.