A market shortage can be caused by a change in any of the demand determinants or supply determinants. An increase in demand or a decrease in supply does the job. A shortage also can be imposed on a market through government intervention, especially by establishing a price ceiling below the equilibrium price.

Working the Market

The Shortage

The equilibrium, found at the intersection of the negatively-sloped demand curve and positively-sloped supply curve is at a price of 50 cents and a quantity of 400 tapes. Equilibrium, however, is not the primary point of interest. The interest lies in disequilibrium and shortage.

A shortage emerges at any price below the equilibrium price of 50 cents. A prime candidate to generate a shortage is a price of 30 cents. Click the [Shortage] button to illustrate the resulting shortage.

• Quantity Supplied: At 30 cents, the quantity supplied is only 200 tapes. Because the price is relatively low, sellers are guided by the law of supply and are not willing and able to offer much of the good for sale.


• Quantity Demanded: However, at the same 30 cent price, the quantity demanded is 600 tapes. At this relatively low price, buyers act according to the law of demand and are willing and able to buy a great deal of the good.


• The Shortage: The end result is that the quantity demanded exceeds the quantity supplied by 400 tapes. As such, the shortage at 30 cents is 400 tapes. Of course, a different price generates a different shortage.

Then What?

Eliminating the Shortage

Because buyers are not satisfied with this shortage, because they cannot buy all of the tapes that they are willing and able to buy at 30 cents each, they are motivated to offer a higher price, to induce sellers to part with a larger quantity. Click the [Price Rise] button to illustrate what occurs.

What happens as this price rises?

• Increase in Quantity Supplied: According to the law of supply, a higher price induces an increase in the quantity supplied. This is just the sort of thing that the buyers hope happens when they offer a higher price. They want a larger quantity supplied.


• Decrease in Quantity Demanded: However, according to the law of demand, a higher price also induces a decrease in the quantity demanded. Buyers who demand a large quantity at the 30 cent price are inclined to reduce their quantity demanded as the price rises.


• No More Shortage: The increase in the quantity supplied and the decrease in the quantity demanded both act to eliminate the shortage. Best of all, as long as any shortage exists, the price continues to rise, and the shortage shrinks. The price stops rising ONLY when it reaches 50 cents, which is the equilibrium price, the price that generates the same quantity demanded as supplied. It is the price that does not have a shortage.