The goods sold in the final weeks of the year were ordered in spring. That long gap between the decision and the sale explains much of what happens at the end of a season.
Manufacturing and shipping consume the lead time
Goods made overseas need factory capacity booked, production run, containers loaded and a sea voyage completed. Each stage takes weeks and none can be compressed cheaply.
Add customs clearance, inland transport and distribution to stores, and the chain from order to shelf routinely runs to several months.
Working backwards from a date in December therefore lands the buying decision somewhere in spring, which is when the commitments are actually made.
Forecasts are made with the wrong information
A buyer choosing quantities in spring is forecasting demand for a period whose economic conditions, weather and fashions are all unknown.
The main evidence available is last year's performance, which is a reasonable guide in stable conditions and a poor one after any disruption.
Error is therefore built into the system. The question is not whether the forecast will be wrong but in which direction and by how much.
Over-ordering and under-ordering fail differently
Too little stock means lost sales that cannot be recovered, because the demand does not wait and a competitor captures it.
Too much stock means markdowns, which cost margin but still convert inventory into cash.
Given that asymmetry, buyers lean towards ordering generously, and the predictable consequence is surplus at the end of the season.
Warehousing costs push the timing
Stock arriving early has to be stored, and storage costs money for every week it sits. Stock arriving late misses the selling window entirely.
The delivery schedule is tuned to arrive as late as safely possible, which is why shipping disruptions have such visible effects on seasonal availability.
It also explains why a sold-out seasonal line is rarely restocked. The replenishment would arrive after the season it was made for has ended.
The season ends on the calendar, not on demand
Seasonal goods lose most of their value on a fixed date whether or not they have sold, because the occasion they were made for has passed.
Holding them for a year costs storage and ties up capital, so clearing them immediately at a steep discount is usually the better commercial choice.
That decision, made months earlier when the order was placed, is what produces the sharp markdowns that follow every seasonal peak.