The determination of equilibrium market prices explains how the interaction between demand and supply determines the price and quantity of goods and services traded in a market. Equilibrium occurs where quantity demanded is equal to quantity supplied, meaning there is neither a shortage nor a surplus. Understanding equilibrium is essential for A-Level Economics students because it provides the foundation for analysing how changes in demand and supply affect market prices and quantities. It is also important for understanding how markets respond to shortages, surpluses and changes in economic conditions.
This topic can be found in:
- AQA A-Level Economics | Component 1: Individuals, Firms, Markets and Market Failure | Topic 3: Price Determination in a Competitive Market
- Pearson Edexcel A-Level Economics B | Theme 1: Markets, Consumers and Firms | Topic 3: Introducing the Market
Definitions
- Equilibrium: The point where quantity demanded is equal to quantity supplied
- Equilibrium Price: The price where quantity demanded is equal to quantity supplied
- Equilibrium Quantity: The quantity bought and sold at the equilibrium price
- Excess Demand: A situation where quantity demanded is greater than quantity supplied
- Excess Supply: A situation where quantity supplied is greater than quantity demanded
Key Features
Market Equilibrium
Market equilibrium occurs where the demand and supply curves intersect, meaning quantity demanded is exactly equal to quantity supplied. The equilibrium price is the market-clearing price because consumers can purchase the quantity they want and producers can sell the quantity they produce. There is no tendency for the price to change because there is neither excess demand nor excess supply. For example, if consumers want to buy 1,000 units of a product and firms are willing to supply exactly 1,000 units at £10, the market is in equilibrium at a price of £10 and a quantity of 1,000 units.
Excess Demand and Excess Supply
When the market price is below equilibrium, quantity demanded is greater than quantity supplied, creating excess demand or a shortage. Consumers compete for the limited goods available, putting upward pressure on price. As the price rises, quantity demanded falls while quantity supplied rises, moving the market towards equilibrium. When the market price is above equilibrium, quantity supplied is greater than quantity demanded, creating excess supply or a surplus. Firms may reduce prices to clear unsold stock, causing quantity demanded to rise and quantity supplied to fall until equilibrium is restored.
Changes in Equilibrium
Equilibrium is not fixed because changes in demand and supply cause the equilibrium price and quantity to change. An increase in demand usually causes both equilibrium price and quantity to rise, while a decrease in demand usually causes both to fall. An increase in supply generally causes equilibrium price to fall and equilibrium quantity to rise, while a decrease in supply causes price to rise and quantity to fall. If demand and supply change simultaneously, the final effect depends on the size and direction of each shift. For example, rising demand for housing can increase both house prices and the number of homes sold, while an increase in the supply of homes can reduce prices and increase the quantity traded.
Evaluation
Advantages
- Explains market prices: The equilibrium model provides a clear explanation of how the interaction between demand and supply determines market prices and quantities
- Shows how markets adjust: The model demonstrates how shortages and surpluses create pressure for prices to change until the market moves towards equilibrium
- Useful for economic analysis: Equilibrium analysis allows economists to predict how changes in demand and supply may affect prices, output and the allocation of resources
Disadvantages
- Markets may not reach equilibrium immediately: Prices and quantities may take time to adjust, meaning markets can experience shortages or surpluses for significant periods
- Other factors can affect prices: Government intervention, market power, information problems and external factors can prevent prices from being determined entirely by demand and supply
- Changes can be difficult to predict: When demand and supply change at the same time, the final effect on equilibrium price and quantity depends on the relative size of the shifts
Summary
- Equilibrium occurs where quantity demanded equals quantity supplied
- The equilibrium price is the market-clearing price where there is no shortage or surplus
- Excess demand creates upward pressure on price
- Excess supply creates downward pressure on price
- Changes in demand and supply cause changes in equilibrium price and quantity
0 comments