A garment sells out in the middle sizes within days and remains available at the extremes for months. This reflects a buying decision made long before the item went on sale.
The size curve
Retailers order stock across sizes according to a projected distribution, generally weighted toward the middle of a range.
That curve is based on historical sales data, which is itself shaped by what was previously stocked, which produces a self-reinforcing pattern.
If the extremes are under-ordered, they sell out or never appear, sales data shows low volume in those sizes, and the next order is weighted further toward the middle.
Which is a documented mechanism and it explains why size availability at the edges of ranges has been persistently poor.
The broken size run
The retail term for what a buyer encounters.
Once the popular sizes are gone, the remaining stock is unsellable at full price to most customers, and the item is marked down.
Which means clearance racks are disproportionately composed of the sizes that were over-ordered relative to demand.
For anybody whose size is in that group, clearance is genuinely productive. For anybody in the middle of the range, it mostly is not.
The extended range problem
Where the pattern is most visible.
Retailers have expanded size ranges considerably in recent years, and availability at the extended sizes is frequently online-only, in fewer styles, and in smaller quantities.
Which produces the situation where a range is advertised as inclusive and the practical experience of shopping it is not.
The commercial explanation is order quantity and the risk of unsold stock in sizes with less historical data.
The consequence is that the data continues to be thin, which sustains the caution, which is the same loop.
Grading and why fit degrades
A technical factor that compounds the availability problem.
Patterns are scaled from a base size using grading rules, and bodies do not scale proportionally.
Which means garments fit best near the base size and progressively worse away from it, unless the maker uses multiple base patterns.
Doing that costs more, and it is what distinguishes brands whose extended sizing works from those whose does not.
The practical signal is whether a brand publishes different fit models or block information for different parts of its range, which some do and most do not.
Restocking
Worth understanding since it determines whether waiting is useful.
Fashion items are generally bought once for a season and not restocked, since the range moves on.
Basics and continuity lines are restocked, sometimes continuously.
Which means an out-of-stock fashion item is generally gone permanently, and an out-of-stock basic will probably return.
Sign-up alerts for restocking work for the second category and rarely for the first.
The return effect
A source of stock that is easy to miss.
Returned items are restocked, which means sizes reappear intermittently after selling out, particularly in the days following a promotional period.
Checking again a week or two after an item sells out is genuinely productive and is not something most people do.
For online retailers with high return rates in apparel, this is a meaningful second chance.
What this means practically
Buy early if your size is in the middle of the range, since waiting means it will be gone.
Wait if your size is at either extreme, since it will be discounted and will still be there.
Check back after sell-out for returns.
And note which brands actually stock your size across their range rather than in a token selection, since that is a durable characteristic of a retailer rather than a per-item accident.
The measurement point
Which underlies all of it.
Since sizes are not standardised, knowing your own measurements and reading brand size charts is the only reliable method.
Recording which nominal size fits at each brand you buy from turns an unreliable system into a usable one.
It takes one afternoon and it eliminates most of the return volume that makes this category expensive for everybody.
The vanity sizing complication
Which interacts with everything above.
Because nominal sizes have drifted and differ between brands, the size that sells out at one retailer is not the same physical size that sells out at another.
Which means the pattern is about each brand's own curve rather than about bodies, and it explains why your experience of availability differs between retailers even at the same nominal size.
Recording your actual measurements, and the size that fits at each brand, is the only way to navigate it.
Pre-orders and drops
A mechanism that partly addresses the size curve problem.
Where a brand takes orders before producing, it manufactures to actual demand rather than to a forecast, which eliminates both the broken size run and the unsold stock.
The trade is waiting, frequently several weeks, and a commitment made before seeing the item.
Smaller brands use this extensively because it removes the capital risk of holding inventory, and it produces a genuinely better outcome on size availability for anybody willing to wait.