This document discusses competitive dynamics and strategies for different stages of a product life cycle. It describes hypothetical market structures and ways companies can expand their total market or protect existing market share through strategies like lowering prices, advertising, and product innovation. The stages of the product life cycle are growth, maturity, and decline, and the document provides example marketing strategies for each stage, such as improving products in growth and targeting new customer segments in maturity. Finally, it discusses how companies may need to modify their brand, products, or marketing programs over time to maintain relevance.