Market Equilibrium, Shortage and Surplus
Where the two curves cross, the amount buyers want matches the amount sellers offer and the market clears. Away from that price a shortage or a surplus builds up, and what disappointed buyers and stuck sellers do next is the pressure that pushes the price back.
What a learner can do afterwards
- Find the equilibrium price and quantity on a diagram and check that the two quantities match there
- Predict a shortage or a surplus from a price set below or above equilibrium and say who is left disappointed
- Explain the pressure that returns the price to equilibrium in terms of what buyers and sellers actually do
1 · Read
The demand and supply schedules meet where quantity demanded equals quantity supplied. For example, buyers plan to buy 8 loaves and sellers plan to sell 8 at one price. On the curves, this is the crossing: the equilibrium price and quantity. The market clears, with no shortage or surplus. This standard model holds other influences fixed.
In the standard model, demand slopes down and supply slopes up. Above equilibrium, quantity supplied exceeds quantity demanded, leaving a surplus. Below equilibrium, quantity demanded exceeds quantity supplied, creating a shortage. Some buyers cannot buy what they want at that price. Compare quantities, not the number of buyers and sellers: one seller can offer many loaves.
If prices can adjust, a surplus gives sellers a reason to cut prices to clear stock. During a shortage, buyers may bid more and sellers may raise prices. These pressures move price toward equilibrium. A fast sellout alone does not prove a shortage. You also need buyers who are willing and able to pay the stated price but cannot get tickets.
A price ceiling is a legal maximum. It is binding below equilibrium and creates a shortage in this model. A price floor is a legal minimum. It is binding above equilibrium and creates a surplus. A ceiling above equilibrium or a floor below it leaves the equilibrium price available.
At equilibrium, planned quantities match. Shortages and surpluses put pressure on flexible prices.
The rewritten readings were written for this dataset.
More to read
When buying and selling match
At an equilibrium price, the amount buyers want matches what sellers offer. Buyers wanting 8 loaves match sellers offering 8, leaving neither a shortage nor a surplus. Under the standard model, prices above equilibrium produce more units offered than wanted. Below equilibrium, more are wanted than offered. Compare units, not buyer or seller totals: each person may trade several.
Limits on price changes
With flexible prices, surplus goods encourage discounts. A shortage may prompt buyers to offer more or sellers to charge more. A ceiling below equilibrium blocks a rise to equilibrium; a floor above equilibrium blocks a fall to it. Such limits are binding. This assumes competitive markets and unchanged outside influences. A fast sellout alone does not prove shortage. There must still be buyers willing and able to pay that price who cannot obtain the goods.
2 · Watch
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Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.