# A Coordinated Supply Contract for a Two-Echelon Supply Chain Considering Learning Effects
## 2 Literature Review
### The Application of Learning Effect to Supply-Chain Management
#### 2.2.2 Supplier Selection and Outsourcing  
Supplier selection is a multifaceted process that requires a consideration of learning effects for optimizing procurement, negotiations, and understanding shared supplier dynamics. [PERSON] [46] underscores the significant influence of learning effects on buyer decisions when selecting suppliers, emphasizing the need to consider how learning reduces production costs and the ability to negotiate with the supplier over residual value. [PERSON] et al. [47] explore the interaction between spillover effects, competition, and investment returns from shared suppliers on investment thresholds and leader investment time, further emphasizing the importance of considering these factors comprehensively in the supplier-selection process. [PERSON] et al. [31] examine factors leading to single-sourcing, dual-sourcing, or hybrid-sourcing strategies under production learning and process improvement to determine the optimal purchasing strategy. Meanwhile, [PERSON] and [PERSON] [32] analyze the optimal order decisions considering supplier characteristics, learning effects, and disruption factors in a dual-sourcing scenario. Integrating learning effects into outsourcing decisions is crucial for understanding cost dynamics and competitive scenarios. Production learning and process improvement can help to determine the optimal outsourcing strategy and supplier configuration decision [24]. The impact of cost-learning effects on strategic manufacturers' outsourcing decisions is examined within a two-period game, underscoring the significance of cost-learning effects in the outsourcing decision-making process [23; 24]. [PERSON] et al. [25] build a two-period model to investigate the competition effect of learning-by-doing in a supply chain with two competing manufacturers. Scheduling and Line-Balancing DecisionsScheduling is the process of arranging and organizing tasks within a defined timeframe. The decrease in production time due to the learning effect has a significant impact on the efficiency of scheduling. [PERSON] et al. [27] extensively review scheduling problems under the learning effects. They classify the learning curve models into two main categories: position-based learning effects and sum-of-processing-time-based learning effects. [PERSON] and [PERSON] [28] propose scheduling classification schemes under different learning effect models. Their studies highlight how learning effects significantly optimize scheduling in various production scenarios, emphasizing efficiency gains in low-volume, high-mix production and addressing challenges in simple assembly lines. Learning effects play a vital role in assembly lines during the new product launch or the start of production [30]. [PERSON] [30] and [PERSON] [32] examine the operation and balancing problems of simple assembly lines by considering learning effects. PricingThe learning effect and pricing strategy are closely intertwined. [PERSON] et al. [15] examine the impacts of the learning effect on pricing strategies and channel efficiency in a decentralized supply chain consisting of a manufacturer and a retailer. It is assumed in their model that the demand is certain, only dependent on the sales price. They investigate two pricing strategies: open-loop (with given wholesale prices) and feedback pricing (with dynamic wholesale pricing) strategies. It is shown that the channel efficiency with the feedback pricing strategy is higher than that with the open-loop strategy. However, their models do not lead to supply chain coordination. [PERSON] et al. [16] examine the impact of learning effects under dynamic pricing, price commitment, and price matching. They present a different perspective, suggesting that production-learning effects may only sometimes be beneficial for companies due to increased expected cost reductions and significant incentives for strategic customer waiting.