Does more demand for notebooks leave the quantity supplied unchanged?

Verdict. The statement is false. A rise in demand for notebooks does raise the quantity demanded in the new equilibrium, but it raises the quantity supplied as well: the price goes up and sellers respond by offering more. What stays unchanged is supply (the supply curve), not the quantity supplied.

Two pairs of terms.

• A rise in demand is a shift of the whole demand curve to the right, caused by a factor other than the good's own price, such as higher incomes; buyers want more at every price. A change in quantity demanded is a move along a given curve.
• Likewise, supply is the whole schedule of amounts offered at different prices, while quantity supplied is the amount offered at one particular price. A change in the good's own price moves sellers along the supply curve: a higher price raises the quantity supplied, an expansion of supply, with no shift of the curve.

What happens in the notebook market. Our own figures for a city market, with the supply curve sloping upward:

• At first the market clears at ₹30 a notebook, with 50,000 notebooks a month demanded and supplied.
• A new school session begins, and at ₹30 buyers now want 62,000. At the old price there is an excess demand of 12,000 notebooks.
• Some buyers are willing to pay more, so the price starts rising. As it rises, sellers move up their unchanged supply curve and offer more notebooks, while buyers move up the new demand curve and want somewhat less than 62,000.
• The price stops rising when the two quantities are equal again, say at ₹33 with 56,000 notebooks.

A rightward shift in demand with supply unchanged raises both the equilibrium price and the equilibrium quantity. Since quantity demanded equals quantity supplied in equilibrium, the quantity demanded cannot rise while the quantity supplied stays put: every extra notebook bought has to be offered by some seller.

The one moment when the statement fits. Only at the old price, just after demand rises and before the price has adjusted, is the quantity demanded higher (62,000) while the quantity supplied is unchanged (50,000). That gap is the excess demand which pushes the price up, so it does not last.

With free entry of firms. If firms can enter and exit the market freely, a rise in demand leaves the equilibrium price unchanged but raises the equilibrium quantity and the number of firms. The quantity supplied rises here too, because new sellers come in.

Conclusion. False. A rise in demand raises the quantity demanded and the quantity supplied together: through the higher price, by a movement along the unchanged supply curve, or, with free entry, through new firms coming in. The statement mixes up an unchanged supply curve with an unchanged quantity supplied.