Optimal multi-item fill rate determination for spare parts

We consider four existing methods in order to determine individual fill rates when a global target fill rate has been established. Given the drawbacks of these approaches, needing numerical optimization and especially unsuitable in the context of spare parts, we present a new approach which provide a closed form formula more focused on the characteristics of these items. This novel approach is validated with a dataset of spare parts of an airline company and outperforms the previous methods. Extensions of our results are also indicated.