Life cycle models are not just a phenomenon of the life sciences. Industries experience a similar cycle of life. Just as a person is born, grows, matures, and eventually experiences decline and ultimately death, so too do industries and product lines. The stages are the same for all industries, yet every industry will experience these stages differently, they will last longer for some and pass quickly for others. Even within the same industry, various firms may be at different life cycle stages. A firms strategic plan is likely to be greatly influenced by the stage in the life cycle at which the firm finds itself. Some companies or even industries find new uses for declining products, thus extending their life cycle. The growth of an industry's sales over time is used to chart the life cycle. The distinct stages of an industry life cycle are: introduction, growth, maturity, and decline. Sales typically begin slowly at the introduction phase, then take off rapidly during the growth phase. After leveling out at maturity, sales then begin a gradual decline. In contrast, profits generally continue to increase throughout the life cycle, as companies in an industry take advantage of expertise and economies of scale and scope to reduce unit costs over time