Order aggregation reduces the effective fixed cost attributable to each individual product or trading partner. Ordering and transportation frequently contain costs that are incurred per replenishment event rather than in direct proportion to the quantity of one particular SKU. Examples include purchase-order processing, truck dispatch, shipment administration, loading, and certain receiving activities. When several products, suppliers, or retail destinations are consolidated into one replenishment movement, those fixed costs are shared across the combined order rather than being borne by one item.

This cost-sharing effect changes the economic lot-sizing trade-off. Because the effective fixed ordering or transportation cost associated with each product becomes smaller, the supply chain can replenish each individual item in smaller quantities without causing an excessive increase in ordering cost. Smaller lots consequently reduce average cycle inventory and associated carrying cost while retaining transportation economies.

This is precisely why aggregation is an important cycle-inventory lever: it preserves economies of scale at the shipment level while allowing smaller product-level replenishment quantities. The underlying principle is also reflected in established supply-chain lot-sizing material, where aggregation spreads fixed ordering and transportation costs across multiple products or supply-chain entities.

Reference Topic: Inventory and Warehousing — Cycle Inventory, Lot Sizing, and Order Aggregation.

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