Detailed Notes on Supply and Demand

Supply and Demand Overview

• In this lecture based on Chapter 2 of Perloff's ‘Microeconomics’, the main topics are:
  • Demand
  • Supply
  • Market Equilibrium
  • Shocking the Equilibrium
  • Effects of Government Interventions
  • When to Use the Supply-and-Demand Model

Demand

• Determinants of Demand:
  • Consumers' purchasing decisions based on several factors:
  • Tastes
  • Information
  • Prices of other goods
  • Income
  • Government actions

The Demand Curve

• Quantity Demanded: Amount consumers are willing to buy at a specific price, holding other factors constant.
• Demand Curve: Depicts quantity demanded at each price point, illustrating consumer responses to price changes.
  • A downward slope indicates:
  • Higher prices lead to lower quantity demanded.
  • Lower prices lead to higher quantity demanded.
• Movement vs. Shift: Changes in price lead to movement along the curve, while changes in other factors result in a shift of the curve.

Factors Affecting Demand Shifts

• Substitutes: Goods consumed instead of others.
• Complements: Goods consumed together.
• Income fluctuations impact purchasing power.
• Tastes and preferences can change due to trends or information.

Demand Function

• Demand Function Formula:
  $Q<em>D = f(p, p</em>s, Y)$
  Where:

  • $Q_D$ = Quantity demanded (millions of tons)
  • $p$ = Price of coffee (dollars per lb)
  • $p_s$ = Price of sugar (dollars per lb)
  • $Y$ = Average income in high-income countries (thousands of dollars)

• Example of Demand Function for coffee:
  $Q<em>D = 8.56 - 0.3p + 0.1p</em>s$

• Summing Demand Curves: Total quantity at a given price is the sum of quantities demanded by each consumer:
  $Q<em>D(p) = Q</em>1 + Q_2$

Supply

• Determinants of Supply:
  • Firms base their production decisions on:
  • The price of the good
  • Costs of production
  • Government regulations

The Supply Curve

• Quantity Supplied: The amount producers plan to sell at a specific price, holding constant other influencing factors.
• Supply Curve: Illustrates quantity supplied at different price points.
  • An upward slope indicates:
  • Higher prices result in larger quantities supplied.
  • Lower prices result in smaller quantities supplied.

Supply Function

• Supply Function Formula:
  $Q<em>S = g(p, p</em>c)$
  Where:

  • $Q_S$ = Quantity supplied (millions of tons)
  • $p$ = Price of coffee (dollars per lb)
  • $p_c$ = Price of cocoa (dollars per lb)

• Example of Supply Function:
  $Q<em>S = 9.6 + 0.5p - 0.2p</em>c$

• Summing Supply Curves: Total supply curve shows total quantities produced by all suppliers at each price level.

Market Equilibrium

• Definition of Equilibrium:
  • A situation where no participant (consumer or producer) has an incentive to change behavior.
  • Equilibrium Price: Where the quantity demanded equals quantity supplied.
  • Equilibrium Quantity: Quantity bought and sold at equilibrium price.

Determining Equilibrium Graphically

• To determine equilibrium, analyze excess supply and excess demand visually on a graph.
• Excess demand and supply can indicate a need for price adjustments.

Mathematical Determination

• Demand and Supply equations can be set equal to find equilibrium:
  • Demand: $Q_D = 12 - p$
  • Supply: $Q_S = 9 + 0.5p$
  • Equilibrium occurs where both are equal. Plugging values gives the solution for equilibrium price and quantity.

Market Dynamics

• Disequilibrium: Occurs when quantity demanded does not equal quantity supplied.
• Excess Demand: Quantity demanded exceeds quantity supplied; results in upward pressure on price.
• Excess Supply: Quantity supplied exceeds quantity demanded; results in downward pressure on price.

Shocking the Equilibrium

• Equilibrium shifts occur due to changes in factors like tastes, income, or government policies, moving the demand or supply curves.

Effects of Government Interventions

• Government actions can:
  • Shift supply or demand curves.
  • Create price controls (ceilings or floors), leading to excess supply or demand.
  • Policies may not align with market equilibrium, causing inefficiencies.

Key Concepts and When to use the Supply-and-Demand Model

• The model applies under conditions where:
  • Participants are price takers.
  • Firms sell identical products.
  • All agents have full information.
  • Transaction costs are low.