Managing flexibility in supply chains: mathematical analysis of dual sourcing systems

Abstract

The COVID 19 pandemic forced supply chain managers to explore different ways to cope with rapid changes in supply, manufacturing, distribution and demand. The lessons learnt from that experience is that flexibility in responding to demand and modularity must be planned at every stage. Along with planning we argue that execution becomes challenging and is equally important to consider when making plans. We illustrate with a broad category of flexibility and modularity, dual sourcing, and how management mathematics can be used to manage these systems and understand the cost of execution. Dual sourcing has been used to manage the trade-off between cost and responsiveness by firms and has received considerable attention in academic literature. It is known that except in special cases, the optimal sourcing policy does not have an easy structure that is practically appealing and can be used by managers. Over the last decade and half, researchers have developed various management mathematics techniques and analyzed the performance of heuristic policies. This paper presents a discussion of the results in a few key papers related to the dual sourcing inventory management problem and recent distribution free results in asymptotic regions. The asymptotic regimes considered include systems where the lead-time from the slower supplier is significantly higher than that from the closer, faster supplier, and conditions where the unit cost of procurement is significantly higher compared to the unit cost of carrying inventory. These regimes represent different conditions about how valuable or costly using the faster supplier is and illustrate the value of simple heuristic policies and characterize the cost of these heuristics. The key learnings are that optimal ordering decisions may be robust to misspecification of demand distribution and managers only need summary statistics such as the average and standard deviation of demand to determine the order quantities from the different suppliers. Managers could also consider ways to roll out new planning and control systems for managing multiple suppliers.