The A9 Algorithm: Availability

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Availability refers to whether or not your product is available right now on Amazon and if it is available for Prime. Additionally, availability is strongly tied to your “in stock history.” But why is this important? Let’s take a look at how Amazon’s A9 uses your availability to determine rank.

Product Availability

If you run out of stock, your listing may drop in rank or disappear altogether. It’s important to Amazon that you are able to keep up with market demand.


Because Amazon wants to make sure that its users are getting the product they are looking for. If your product is hit or miss when it comes to inventory, Amazon can’t trust that shoppers will be able to find what they are looking for.

Amazon Prime Products

Product availability becomes even more important for Amazon Prime sellers. Because Prime is a proven service, and so many Amazon customers trust the Prime label, Amazon will penalize Prime sellers who can’t fulfill.

Keeping track of inventory is especially important for Prime sellers who choose to fulfill orders themselves rather than taking advantage of Amazon fulfilled orders. Prime orders have to be shipped on the same day!

If you can’t stay stocked or you can’t deliver on time, your BSR (best seller rank) may drop and impact your ability to retain Prime status.  

Inventory History

Amazon tracks your inventory history, and they measure your ability to stay stocked. This measurement takes into account the quantity of product that you move and how long you stay out of stock. The more product you move and the more you stay stocked, the higher you can rank. Amazon penalizes you for having a history of running out of stock.


Sellers should pay close attention to when they need to restock. You definitely don’t want to run completely out, but when should you restock your inventory?

We recommend restocking your inventory in advance. Don’t wait until your product will run out in a few days. Stay on top of your inventory and be proactive.

A better question, however, might be: how much inventory should you restock your listing with? Adding a large number of units (over 150 units or so) can give you a big restocking boost compared to adding a few units here and there.

Additionally, we recommend creating an FBM condition for your products. An FBM condition works as a backup listing that kicks in when your FBA inventory runs out of stock. As long as you have the ability to fulfill your own products, this is a great way to make sure you never run out of stock.

You can create an FBM condition under “Manage Inventory” and then by clicking “Edit” → “Add another condition” as shown in the image below.

For more information on best practices on product availability, our Amazon experts would be happy to make specific recommendations for your e-commerce business. Contact us today!


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