What metric should you watch when you are only shipping items using the Fulfilment by Amazon program?

The Inventory Performance Index (IPI) is the most relevant metric when exclusively using Fulfilment by Amazon (FBA). IPI measures your overall FBA inventory performance, reflecting how efficiently you manage your inventory, including sales volume, excess inventory, and in-stock rates. A higher IPI score indicates better inventory health, which can lead to lower storage fees and improved visibility. Late Shipment Rate is not applicable because Amazon handles shipping for FBA orders. A-Z Claims are customer service issues that can arise regardless of fulfillment method, but they don't specifically measure inventory performance.