What appears to be a regular cycle in the sales of products has been identified for many products. Because of its resemblance to the cycle of human life, this cycle is referred to as the product life cycle. The product life cycle can be summarized as follows: in the first stage, a product is ‘born’ or introduced to the market. In the next stage, it goes through a rapid growth stage. In the third stage the product reaches maturity. Finally in the fourth stage, the product declines and disappears. This cycle has been of great interest in both marketing and economics.