Inventory teams rank products by units or revenue because that’s what the stock report shows. Retention needs a second column: of the orders containing this product, what share come from customers who have bought from you before?

Two products, same sales

Say a brand ships 10,000 orders a month and sells two products at about 2,500 units each. The starter kit is in most first orders: 85% of its orders come from new customers. The refill is the opposite: 80% of its orders come from customers on their second order or later. The stock report treats them as twins. A three-week stockout on each is not the same event.

• Starter kit out: mostly new visitors see “sold out.” Some leave, and ad spend is wasted until it’s back. Painful, and visible the next morning.
• Refill out: about 2,000 customers due to reorder can’t. Some wait, some buy elsewhere and don’t come back. Much of the cost lands months later, in orders that never happen.

If both are running low and you can only air-freight one, the answer depends on the second column.

The repeat share of a product

For each product, count the orders containing it over the last 90 days, and the share placed by customers who had ordered before. That’s its repeat share. Sort by repeat orders (orders times repeat share) instead of by units, and read the top of the list. It’s usually refills, consumables, basics in a customer’s size and anything bought on subscription. The query is in Appendix A.

Then weight stock cover by it. A product with high repeat share and three weeks of cover is a bigger risk than a new-customer product with one week. The tool below turns one product’s numbers into a daily cost of being out, split into the part you’ll see this month and the part you won’t.

With the defaults, a three-week stockout hits 600 orders and costs about $19,080: $7,200 in contribution lost that month and $11,880 in future contribution from repeat customers. That’s about $909 a day, and 62% of it never appears in a lost-sales report Derived. Run the same numbers for a product with a 15% repeat share and the future part falls to under a third.

What to do with the ranking

1. Set cover by tierGive the top of the repeat list more weeks of safety stock than units alone would earn, and pay for it by holding less on products bought mostly by new customers.
2. Use cost per day as the expedite ruleWhen a top repeat product is heading out, the daily cost from the tool is the most you should pay per day saved. It turns an argument about air freight into arithmetic.
3. Point new traffic elsewhere when cover is thinIf a product is down to its last weeks, stop sending paid traffic to it and save what’s left for the people who reorder it. A new visitor who meets “sold out” costs you an ad click; a regular who meets it costs you part of a year.

Do this

• Add a repeat-share column to the stock report this week, and sort by repeat orders. Run the tool for the top three products and put their cost per day next to their weeks of cover.