The sales of a company are the part of the total sales of industry. If the conditions of industry changes then the sales of each of the firm in the industry is affected. All teh times the new marketers enter the market and some eclipse. It is also to be decided about the position of our firm in the industry whether it has the leadership status or follower status or challenger status. Change in other factors by one firm also affects the status of another. For example if the prices of the product by a firm are reduced than there is an impact on other firms. Same is the case with promotion and distribution. All these factors affect the demand forecasting of the product.