An Announced Change Pulls Demand Forward

Announcing a change ahead of time creates a deadline, and deadlines rearrange demand. The behaviour that follows is predictable enough to plan around, and it rarely favours waiting until the last week.

A known deadline converts later buyers into earlier ones

People who would have bought over several months compress into the period before the change. The total quantity is similar; the timing is not.

Sellers know this is coming and prepare for it, which is why promotional activity clusters ahead of announced changes rather than during them.

The concentration is entirely a function of the announcement. An unannounced change produces no such pattern.

Concentrated demand exhausts the popular options first

Stock is ordered against a forecast made before the announcement. Demand arriving early empties the most-wanted variants and leaves the rest.

Late buyers therefore face a narrower choice at the same or higher prices, which is the opposite of the usual pattern where waiting widens choice.

Availability, rather than price, is usually what bites first in these episodes.

The slump afterwards is the mirror image

Once the deadline passes, demand falls below normal, because the buyers who would have appeared have already bought.

Sellers holding stock into that period face a quiet market and often discount to clear it, which makes the weeks after a deadline a better time to buy than the weeks before.

This applies whether or not the change itself made the goods more expensive, since the effect comes from the timing shift rather than the change.

Prices can move before the rule does

Sellers facing a known increase in their own costs sometimes adjust early, spreading the change rather than applying it in one step.

This means the saving from buying before a deadline is often smaller than the arithmetic suggests, because part of it has already been absorbed into the current price.

Comparing against prices from before the announcement, rather than against the projected future price, shows how much of the movement has already happened.

Where the deadline genuinely matters

For large purchases where the change is substantial, buying ahead can be worthwhile despite the crowd, provided the purchase was going to happen anyway.

Bringing forward a purchase you were not otherwise going to make converts a saving into new spending, which is the usual way these episodes cost households money.

The test is whether the item was already on the list before the announcement appeared.

Where it was not, the deadline is doing the work of persuasion, and the saving is being measured against a purchase that would otherwise never have happened.