Draw the graph · Micro · Supply and demand

A store cuts its own price

QuantityPrice0DSE₀
Ddemand
—
Ssupply
—

Drag a curve sideways, or use its arrows. A curve you do not move is a curve you are saying stays put.

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Demand stays put. Supply stays put.

The only thing that changed is the price of the good itself. A change in a good's own price never shifts its demand curve or its supply curve. It moves buyers along the demand curve, to a higher quantity demanded, and that is all. No curve moves.

Quantity demanded rises along the unchanged demand curve, and neither curve moves.

Common mistake. The most common error in all of supply and demand: shifting demand right because 'people buy more when it is cheaper.' They do, but that is a movement along the curve. Only non-price factors shift demand.

More supply and demand prompts

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Lesson: Shifts in Demand

Every prompt here is one shift. The course chains them: a lesson on why the curve moves, a graded drawing, and spaced review that brings back the shifts you get wrong.