A best seller rarely leaves the first row because it stops selling. It leaves because it sold so well that the popular sizes are gone. What stays behind is a product with strong sales history, a "best seller" position and two sizes that fit almost nobody. This post is about that product, and about how to move it without watching every category by hand.
What "size broken" means
Stock is usually tracked per product: in stock or out of stock. For anything that comes in sizes, that is too coarse. A jacket with XS and XXL left is in stock. For most of the people who see it, it is not for sale.
The measure that captures this is size availability: the share of a product's sizes that are in stock. Six sizes with all six available is full availability. Six sizes with two available is one third.
A product is size broken when that share has fallen so far that most visitors will not find their size. Merchandiser puts the line at 30%: a product with 30% or fewer of its sizes in stock gets the Size Broken badge in the panel.
Why sales history makes it worse
Most sorting, manual or automatic, looks at what sold. Sorting by weekly sales puts last week's winners first, and last week's winners are exactly the products that are running out this week.
The result is a first row that looks good in a report and performs badly on the page. Visitors click the product, open the size selector, find their size greyed out and leave. The product keeps collecting views, which a naive rule reads as more interest, and it holds its position.
The problem is not the sales signal. It is using the sales signal alone.
Sort by demand and availability together
The fix is to let availability scale demand. In a sorting rule, that means multiplying the demand part of the score by size availability:
- A product with strong demand and all sizes in stock keeps its full score.
- A product with the same demand and a third of its sizes keeps a third of it.
- A product that is out of stock falls to the bottom.
This is gentler and more accurate than a hard cut-off. A product with one missing size loses a little. A product with one size left loses most of its position and makes room for something customers can buy.
In Merchandiser, size availability is one of the ranking signals a rule can use, together with stock units and in-stock status. Merchandiser AI applies the same idea without a rule: each prediction is weighted by size availability, so a promising product that has sold out of most sizes ranks below an equally promising one that is fully in stock.
Check the first row, not the average
A collection can have healthy stock overall and a broken first row. What matters is what the visitor sees before scrolling.
That is why the Collection Health Score has a signal for it. Top-of-Page Availability counts how many of the first products of a collection are fully available, meaning in stock and not short of sizes. When the count drops, the collection's score drops with it, and the recommendation is plain: replenish or demote the out-of-stock and size-broken products near the top.
The health page lists every active collection with the lowest scores first, so the categories with a broken first row surface on their own.
Do not let pins undo it
Sorting rules respect pins. That is the point of a pin, and it is also how a size-broken product stays in position one for weeks: someone pinned it for a campaign when it had every size, and nobody came back to unpin it.
Two settings help:
- Auto unpin after a set time. The pin is released once it is older than the period you choose.
- Unpin products that are missing a size. Once any size of a pinned product is out of stock, its pin is released and the product returns to the automatic sort.
The second is strict on purpose. A pin overrides the data, so it should only hold while the product is fully available. More on this in Product Pinning.
When the product is worth restocking
Demoting a size-broken product treats the symptom. Sometimes the right answer is to get the sizes back.
Merchandiser's insights separate the two cases. "Demanded product has limited variant availability" marks a product that customers still look at or buy while most of its sizes are missing. That is a restocking signal for the buying team, not only a sorting problem. A size-broken product that nobody looks at needs no action: the sort has already moved it down.
A short checklist
- Make sure your product feed carries stock per size, not only per product.
- Use size availability in the sorting rule of every collection that sells sized products.
- Review the collections with a low top-of-page availability first.
- Turn on auto-unpin for campaign pins.
- Send the list of demanded, size-broken products to whoever orders stock.