Overview

Recent analysis from Repricer indicates that Amazon merchants who ship orders on the same day or guarantee next‑day delivery enjoy a Buy Box win rate that is roughly 18 % higher than sellers relying on standard, multi‑day fulfillment. The speed of delivery has become a dominant factor in Amazon’s Buy Box algorithm, making fulfillment strategy a critical lever for sellers competing on shared ASINs.

Key Points

• 18 % win‑rate boost — Listings that promise same‑day or next‑day shipping capture the Buy Box at a rate 18 % above those offering five‑to‑seven‑day delivery.
• FBA dominance — When price is held constant, Fulfillment by Amazon (FBA) listings win the Buy Box three to five times more often than merchant‑fulfilled alternatives.
• Seller‑Fulfilled Prime (SFP) parity — Sellers that qualify for SFP can approach FBA win‑rate levels, provided they maintain a 99 % on‑time shipment record.
• Buy Box rotation frequency — The algorithm reassigns the Buy Box multiple times per hour, reacting to changes in price, inventory, and delivery‑speed signals.
• Non‑negotiable performance metrics — Order Defect Rate must stay under 1 %, Late Shipment Rate under 4 %, and Pre‑Fulfillment Cancellation Rate below 2.5 % to remain eligible.

How Delivery Speed Influences the Algorithm

1. Handling‑time assessment — Amazon first looks at the interval between order receipt and actual shipment.

   • Example: A seller who processes orders within 24 hours receives a higher algorithmic score than a competitor who ships after 72 hours, even if both list the same price.

2. Estimated‑delivery date comparison — The projected delivery date displayed to the buyer is weighted heavily.

   • Example: A product advertised with a “next‑day” ETA outranks an identical item promising delivery in five to seven days, leading to a higher probability of Buy Box placement.