## 3 Background
### Product Life Cycle Model  
The Product Life Cycle (hereinafter referred to as PLC) curve represents the sales trajectory of a product over time while it remains on the market. It consists of four fundamental phases, which can be characterized as follows (Figure 2). Start: This phase marks the product's entry into the market, characterized by low sales volumes. As a new product is introduced, a high degree of variability in its parameters can be expected. From a time perspective, it is desirable to keep this phase as short as possible [21]. Growth (Improvement): In this stage, the product gains popularity among customers, gradually becoming well-known and sought after. On the one hand, sales experience the highest growth rate; on the other hand, the variability of product parameters decreases as standardization takes place [21]. Figure 2: The Product Life Cycle (PLC) curve [21]. Maturity: At this point, product sales reach their peak, and the product becomes a standard offering in the market. High competition is expected. Ideally, a product should remain in this phase for as long as possible. Maintaining a competitive edge requires continuous product innovation [21]. Decline (Regress): Sales begin to decline due to innovations introduced by competitors. The product gradually exits the market, leading to production discontinuation. However, from a customer service perspective, it is essential to ensure after-sales support, including warranty services and spare parts availability [21]. The specification of the product life cycle phase is important for the following reasons:  
1. Choosing an appropriate marketing strategy and tools of the marketing mix (4P: Product, Place, Price, Promotion): Understanding the phase in which a product resides helps determine the most effective marketing tactics, including product development, distribution channels, pricing strategies, and promotional activities. 2. Determining the product price: The product's life cycle phase directly influences pricing strategies. In the introduction phase, the price may be set high for early adopters or low to encourage adoption, while in maturity, competitive pricing becomes more critical. 3. Forecasting future sales: Knowledge of the product's life cycle stage aids in predicting future sales patterns. As the product progresses through its phases, businesses can better estimate demand, plan for inventory, and make informed decisions on production and distribution. Additionally, understanding the product life cycle through trend analysis shapes competitiveness decisions, allowing companies to navigate the various stages from introduction to decline. This knowledge informs decisions on product innovation, marketing, and pricing, helping businesses extend product profitability, meet consumer demands more effectively, and strengthen market positioning. The increasing complexity of the environment in which organizations must operate and thrive, along with evolving customer demands, necessitates an understanding of key variables that influence both strategic development and business efficiency. Forecasting serves as a critical tool in reducing uncertainty about future developments. The accuracy and reliability of decisions are significantly influenced by information derived from forecasting methods, as forecasted data directly impact the formulation of an organization's strategic direction. In economics, time series analysis is one of the most fundamental methods for examining economic data. The primary objective of time series analysis is to develop an appropriate model that enables management to make informed predictions for future periods based on historical data. A well-constructed time series model allows for the simulation of time-dependent variables in a manner that minimizes discrepancies between observed values--such as those in financial markets--and values generated by the model. Economic indicators are frequently monitored on a daily, monthly, or quarterly basis.