AQA A-Level Economics (7136) · The Operation of Markets
Specification points
- The determination of equilibrium market prices.
- The functions of the price mechanism: rationing, incentive and signalling.
- How markets and prices allocate resources.
Market equilibrium
Equilibrium occurs where demand equals supply. Above equilibrium there is excess supply (a surplus), which pushes price down; below equilibrium there is excess demand (a shortage), which pushes price up. The market clears at the equilibrium price and quantity.
The functions of the price mechanism
Prices allocate resources through three functions:
- Signalling — prices convey information about scarcity and demand.
- Incentive — higher prices reward producers for supplying more.
- Rationing — higher prices ration scarce goods to those willing to pay.
Rising demand → higher price → signals scarcity → incentivises supply → rations demand → resources reallocated.
Key definitions
| Term | Definition |
|---|---|
| Equilibrium | The price where quantity demanded equals quantity supplied. |
| Price mechanism | The way prices signal, incentivise and ration to allocate resources. |
Shifts and the new equilibrium
Any event is analysed by deciding which curve shifts and reading off the new equilibrium: demand rises → P↑ Q↑; supply rises → P↓ Q↑, and so on. Interconnected markets (substitutes, complements, joint supply, composite demand, derived demand) mean a change in one market ripples into others.
Worked example
A poor harvest cuts the supply of wheat (supply shifts left). The price rises, rationing the smaller quantity, signalling scarcity and giving farmers an incentive to plant more next season. Related markets (bread, animal feed) are affected through higher input costs.
Common exam mistakes
- Confusing a surplus/shortage at a given price with a shift.
- Forgetting to relabel the new equilibrium.
- Listing only one function of the price mechanism.
Exam technique
Draw and label shifts, state the new price *and* quantity, and use the signal-incentive-ration chain to explain reallocation.
Quick revision
- Equilibrium = where D meets S; surpluses/shortages self-correct.
- Price mechanism: signal, incentive, ration.
- Markets are interconnected (substitutes, complements, derived demand).