Multi-echelon inventory optimization (MEIO) models inventory levels across multiple stages of a supply chain. It considers how inventory levels at one stage impact other stages. MEIO can minimize total inventory costs across all stages while meeting customer service goals, unlike traditional approaches that optimize each stage independently. Not using MEIO can lead to excess inventory, stockouts when inventory exists elsewhere, and poor demand forecasting passed between stages. MEIO accounts for factors like demand, lead times, replenishment frequency and service levels that drive inventory needs at each stage.