Nonparametric Safety Stock Dimensioning: A Data-Driven Approach for Supply Chains of Hardware OEMs

TL;DR

This paper introduces a data-driven, nonparametric method for safety stock dimensioning in supply chains that accounts for non-normal, intermittent demand, outperforming traditional models in simulations and optimization.

Contribution

It presents a novel approach using Kernel Density Estimation to determine demand distributions and optimize safety stock levels without assuming normality.

Findings

Outperforms traditional models in simulation.

Achieves desired service levels with lower safety stocks.

Effective for non-normal, intermittent demand patterns.

Abstract

Resilient supply chains are critical, especially for Original Equipment Manufacturers (OEMs) that power today's digital economy. Safety Stock dimensioning-the computation of the appropriate safety stock quantity-is one of several mechanisms to ensure supply chain resiliency, as it protects the supply chain against demand and supply uncertainties. Unfortunately, the major approaches to dimensioning safety stock heavily assume that demand is normally distributed and ignore future demand variability, limiting their applicability in manufacturing contexts where demand is non-normal, intermittent, and highly skewed. In this paper, we propose a data-driven approach that relaxes the assumption of normality, enabling the demand distribution of each inventory item to be analytically determined using Kernel Density Estimation. Also, we extended the analysis from historical demand variability to forecasted demand variability. We evaluated the proposed approach against a normal distribution model in a near-world inventory replenishment simulation. Afterwards, we used a linear optimization model to determine the optimal safety stock configuration. The results from the simulation and linear optimization models showed that the data-driven approach outperformed traditional approaches. In particular, the data-driven approach achieved the desired service levels at lower safety stock levels than the conventional approaches.