Study Notes on Market Equilibrium

DEMAND AND SUPPLY: MARKET EQUILIBRIUM

Market Equilibrium Overview

Market equilibrium is a fundamental concept in economics that deals with the price and quantity established through the interaction of supply and demand. It can be precisely defined as the price in the market at which the quantity that consumers wish to buy equals the quantity that firms wish to supply. This definition is adapted from Sloman, J and Garrett, D (2019).

In graphical terms, the equilibrium in a demand and supply graph is represented by the point where the demand curve intersects with the supply curve.

Equilibrium Price and Output

Monthly Market Demand and Supply of Potatoes

The following data outlines the demand and supply of potatoes measured monthly (in tonnes).

  • Price per Kilo (in pence): 4, 12, 16

  • Total Market Demand (in tonnes): 700 (point A), 500 (point B), 350 (point C), 100 (point D), 200 (point E), 300 (point F)

  • Total Market Supply (in tonnes): Corresponding to price changes (100 (a), 200 (b), 350 (c), 530 (d), 600 (e))

Demand and Supply Graphs

The graphs illustrating the relationship between the price of potatoes (in pence per kg) and the quantity supplied and demanded (in tonnes, denoted as 000s) show various levels and points (A, B, C, D, E):

  • The demand curve slopes downwards, demonstrating that as the price decreases, the quantity demanded increases.

  • Conversely, the supply curve typically slopes upwards, indicating that as the price increases, firms are willing to supply more.

Shortages and Surpluses

  • Shortage: At a price of 4 pence, a demand exceeding supply leads to a shortage (300,000 tonnes). This situation indicates that consumers want more of the product than what is available at that price point.

  • Surplus: Conversely, at a higher price point (12 pence), the quantity supplied surpasses the quantity demanded, resulting in a surplus (330,000 tonnes).

These scenarios reflect how shifts in supply and demand affect the quantity and price equilibrium in the market for potatoes monthly. Each point (A, B, C, D, E) represents a different market condition based on price changes.

Effect of a Shift in the Demand Curve

The demand curve can shift due to various factors such as consumer preferences, income changes, or the prices of complementary goods.

  • Increase in Demand: If there is an increase in consumer demand, reflected in a rightward shift of the demand curve (from D1 to D2), the equilibrium price ($Pe$) and equilibrium quantity ($Qe$) will both increase, leading to a new equilibrium point (Qe1, Pe1).

  • Decrease in Demand: Conversely, a leftward shift in the demand curve (from D2 to D1) indicates decreased demand. The new equilibrium will lead to a decrease in both the equilibrium price and the equilibrium quantity (Qe2, Pe2) as fewer products are demanded at the original price.

Effect of a Shift in the Supply Curve

Just like demand, supply can also shift, which affects equilibrium.

  • Decrease in Supply: A leftward shift in the supply curve (from S1 to S2) reflects a decrease in the quantity supplied. This leads to an increase in the equilibrium price and a reduction in equilibrium quantity (Pe1, Qe1 to Pe2, Qe2).

  • Increase in Supply: A rightward shift of the supply curve (from S1 to S2) shows that suppliers can provide more goods at lower prices. This results in a decrease in price and an increase in the equilibrium quantity (Pe1, Qe1 to Pe3, Qe3).

Examples of Market Equilibrium

Examples where the principles of demand and supply and market equilibrium apply include:

  • House prices, which are affected by demand from buyers and the supply of available housing.

  • Demand and supply for beef, where consumer preferences and production costs create fluctuations.

  • Cocoa prices, influenced by global demand and supply conditions.

  • Butter prices, which can vary based on dairy production levels and market demand.

For further reading, refer to Sloman and Garrett's "Essentials of Economics: Market equilibrium" and Mankiw, G "Microeconomics - Market equilibrium" for deeper insights into these concepts.

Summary

In conclusion, market equilibrium is defined as the price in the market at which the quantity that consumers wish to buy equals the quantity that firms wish to supply, marked by the intersection of the demand and supply curves. Movements in either curve due to various factors lead to changes in the equilibrium price and quantity, resulting in new market conditions.