Sizes XS and S (sizes 0 to 4 in the US) are surprisingly fast selling sizes. More often than not, soon after a sale starts the smallest sizes are in short supply or no longer available, and sale racks are full of sizes M and L. This doesn’t make sense, when the most bought shopping sizes* are usually between an American size 6 and 10. Logically, those are the sizes that should sell out first. Why is this not the case? The reason is quite logical and it takes me back to my fashion buying days – fashion buyers deliberately understock the smallest sizes.

Fashion Buyers are responsible for selecting the items and sizes that sell in a store. They will order in a style from a manufacturer over a very carefully distributed size curve. When they place the order it makes sense to order more of the sizes that are popular, and fewer of the other sizes. So for example, buyers bulk up the order in sizes 6 to 10 because those are the most shopped sizes. That way the store can make the most profit AND offer the most correct size to their customers.

The thing is that they don’t create the size curve to exactly match the popularity of sizes. They order a little less of the unpopular sizes and a little more of the popular sizes. To understand why they do this, consider what happens in practice:

A clothing order hits stores with a full complement of sizes. As the style is purchased, fewer of the sizes become available thereby adjusting the size curve. Because the smaller sizes are intentionally under stocked, they sell out faster than larger sizes (of which there is often two to three times as much quantity). Retailers are happier to sit with an over stocked set of larger sizes than smaller sizes because as time passes by, they have a better chance of selling the larger sizes at any price (full or discounted). Since the most bought shopping sizes are larger than an XS or S, holding surpluses of the larger sizes is less risky at any time of the year.

The bottom line is that they know that their size curve is somewhat of a guess. And they would prefer to err on the low side for less popular sizes and on the high side for more popular sizes. First, one extra item in a popular size is easier to sell, and second, even if they don’t sell it a popular size is easier to sell on down the value chain to a discounter.

That’s why places like TJ Maxx and the Rack are full of size M and L, and sizes 6 to 10. That’s why the smallest sizes are the first to go at Nordstrom Anniversary Sale time. Ever wonder why many thrift and consignment stores are full of sizes 6 to 10? Now you know.

*Note: The most shopped clothing sizes in the US are NOT the same as the average clothing sizes of American women. They are, in fact, a different set of sizes. The average clothing sizes of American women are 12 and 14, yet the most shopped sizes are smaller than that. A topic for another day!