Market Forces: Demand and Supply Study Notes

Overview of Market Forces: Demand and Supply

• Goal of the Chapter: To analyze the fundamental forces of demand and supply, investigate market equilibrium, understand the impact of price restrictions, and apply comparative statics to business scenarios.
• Main Components:
  • Market Demand Curve: Includes the demand function, determinants of demand, and consumer surplus.
  • Market Supply Curve: Includes the supply function, supply shifters, and producer surplus.
  • Market Equilibrium: The intersection of supply and demand.
  • Price Restrictions: Government interventions like price ceilings and price floors.
  • Comparative Statics: Analyzing how changes in determinants affect equilibrium.

Market Demand Curve

• Definition: The market demand curve shows the total amount of a good that will be purchased at alternative prices, while holding all other factors constant.
• The Law of Demand:
  • There is an inverse relationship between price and quantity demanded.
  • The demand curve is characterized as being downward sloping.
  • Visual representation: Price is on the vertical axis, and Quantity ($D$) is on the horizontal axis.

Determinants of Demand

Demand is influenced by several factors beyond the price of the good itself:

• Income:
  • Normal Good: A good for which demand increases as consumer income increases.
  • Inferior Good: A good for which demand decreases as consumer income increases.
• Prices of Related Goods:
  • Substitutes: Goods that can be used in place of one another; an increase in the price of one leads to an increase in demand for the other.
  • Complements: Goods that are used together; an increase in the price of one leads to a decrease in demand for the other.
• Advertising and Consumer Tastes: Marketing efforts and shifts in what consumes prefer.
• Population: Changes in the number of potential consumers in a market.
• Consumer Expectations: Anticipated future changes in prices or income.

The Demand Function

• General Equation: The demand function is represented as $Q_x^d = f(P_x, P_y, M, H)$.
• Variable Definitions:
  • $Q_x^d$: Quantity demanded of good $X$.
  • $P_x$: Price of good $X$.
  • $P_y$: Price of a related good $Y$ (Substitute or Complement).
  • $M$: Income (Normal or Inferior good).
  • $H$: Any other variable affecting demand (e.g., advertising, population, expectations).
• The Inverse Demand Function: Price expressed as a function of quantity demanded.
  • Example Calculation:
    • Given Demand Function: $Q_x^d = 10 - 2P_x$
    • Step 1 (Isolate $P_x$): $2P_x = 10 - Q_x^d$
    • Step 2 (Solve for $P_x$): $P_x = 5 - 0.5Q_x^d$

Changes in Demand vs. Quantity Demanded

• Change in Quantity Demanded:
  • Occurs due to a change in the price of the good itself.
  • Graphically represented as a movement along a fixed demand curve ($D_0$).
  • Example: A price drop from $6$ to $4$ causes an increase in quantity demanded from $7$ to $10$ (Movement from Point A to Point B).
• Change in Demand:
  • Occurs due to a change in a determinant other than price (e.g., income, tastes).
  • Graphically represented as a shift of the entire curve (e.g., from $D_0$ to $D_1$).
  • Example: At a constant price of $6$, a shift from $D_0$ to $D_1$ increases quantity from $7$ to $13$.

Consumer Surplus

• Definition: The value consumers derive from a good that they do not have to pay for. It is the difference between what a consumer is willing to pay and the market price.
• Strategic Importance: Useful in marketing disciplines for strategies involving value pricing and price discrimination.
• Consumer Sentiment:
  • High Consumer Surplus: Associated with statements like "I got a great deal!", "Bang for the buck!", or "Total value greatly exceeds amount paid."
  • Low Consumer Surplus: Associated with statements like "I got a lousy deal!", "Hard bargain!", or "They squeezed every last cent from me."
• Discrete Case Calculation:
  • If a consumer values successive units at $\$8$, $\$6$, and $\$4$, and the market price is $\$2$ per unit:
  • $\text{Consumer Surplus} = (8 - 2) + (6 - 2) + (4 - 2) = \$12$
• Continuous Case Calculation:
  • Calculated as the area under the demand curve and above the price line.
  • Example: Demand starts at $\$10$; at Price = $\$2$, Quantity = $4$.
  • $\text{Total Value of 4 units} = \$24$
  • $\text{Total Expenditure} = 2 \times 4 = \$8$
  • $\text{Consumer Surplus} = 24 - 8 = \$16$

Market Supply Curve

• Definition: Shows the amount of a good that will be produced by firms at alternative prices.
• Law of Supply: There is a direct relationship between price and quantity supplied; as price increases, quantity supplied increases.
• Graphing: The supply curve ($S_0$) is upward sloping.

Supply Shifters

Factors that cause the entire supply curve to shift include:

• Input Prices: Costs of labor, raw materials, etc.
• Technology or Government Regulations: Improvements in production or changes in compliance costs.
• Number of Firms: Entry of new firms (increases supply) or exit of existing firms (decreases supply).
• Substitutes in Production: Alternative goods a firm could produce with the same resources.
• Taxes:
  • Excise Tax: A per-unit tax.
  • Ad Valorem Tax: A percentage tax based on value.
• Producer Expectations: Anticipated future price changes.

The Supply Function

• General Equation: The supply function is represented as $Q_x^s = f(P_x, P_r, W, H)$.
• Variable Definitions:
  • $Q_x^s$: Quantity supplied of good $X$.
  • $P_x$: Price of good $X$.
  • $P_r$: Price of a production substitute.
  • $W$: Price of inputs (e.g., wages).
  • $H$: Other variables affecting supply.
• The Inverse Supply Function: Price as a function of quantity supplied.
  • Example Calculation:
    • Given Supply Function: $Q_x^s = 10 + 2P_x$
    • Step 1 (Isolate $P_x$): $2P_x = 10 + Q_x^s$
    • Step 2 (Solve for $P_x$): $P_x = 5 + 0.5Q_x^s$

Changes in Supply vs. Quantity Supplied

• Change in Quantity Supplied:
  • Movement along the supply curve caused by a change in the price of the good.
  • Example: Price increases from $10$ to $20$, causing quantity supplied to increase from $5$ to $10$ (Point A to Point B).
• Change in Supply:
  • A shift in the entire curve ($S_0$ to $S_1$) caused by a change in a non-price determinant.
  • Example: At a constant price of $\$5$, supply increases from $6$ to $7$ units.

Producer Surplus

• Definition: The amount producers receive in excess of the minimum amount necessary to induce them to produce the good.
• Graphical Representation: The area above the supply curve and below the market price ($P^*$).

Market Equilibrium

• Definition: The price ($P^*$) where quantity supplied equals quantity demanded ($Q_x^s = Q_x^d$).
• Characteristics: No shortage, no surplus; represented as a "steady-state."
• Disequilibrium: Price Too Low:
  • If Price = $\$5$, Supply = $6$ and Demand = $12$.
  • $\text{Shortage} = 12 - 6 = 6$
• Disequilibrium: Price Too High:
  • If Price = $\$9$, Supply = $14$ and Demand = $6$.
  • $\text{Surplus} = 14 - 6 = 8$

Price Restrictions

• Price Ceilings: The maximum legal price that can be charged.
  • Impact: Leads to a shortage since $Q_d > Q_s$.
  • Examples: 1970s gasoline prices, NYC housing, ATM fee restrictions.
• Price Floors: The minimum legal price that can be charged.
  • Impact: Leads to a surplus since $Q_s > Q_d$.
  • Examples: Minimum wage, agricultural price supports.

Full Economic Price

• Formula: $P_F = P_C + (P_F - P_C)$
  • $P_F$: Full economic price.
  • $P_C$: Price ceiling (pecuniary price).
  • $(P_F - P_C)$: Non-pecuniary price (e.g., opportunity cost of time).
• Example: 1970s Gasoline Case Study:
  • Ceiling Price ($P_C$): $\$1$
  • Time spent in line: $3\,hours$ to buy $15\,gallons$.
  • Opportunity cost of time: $\$5/hr$.
  • Total value of time: $3 \times 5 = \$15$.
  • Non-pecuniary price per gallon: $\$15 / 15 = \$1$.
  • Full economic price: $1 + 1 = \$2$

Comparative Static Analysis and Applications

• Definition: Analysis used to determine how equilibrium price and quantity change when a determinant of supply or demand changes.
• Case Study: Decline in PC Component Prices:
  • Scenario 1: Small PC Manufacturer:
    • Event: Component prices fall (Lower input prices for PCs).
    • Impact: Supply of PCs shifts right/down ($S$ to $S^*$).
    • Big Picture: Equilibrium price of PCs falls ($P_0$ to $P^*$); Equilibrium quantity of PCs sold increases ($Q_0$ to $Q^*$).
    • Action Plan: Manage contracts, inventories, human resources, and marketing based on higher volume.
  • Scenario 2: Software Company:
    • Event: Lower PC prices lead to more PCs sold.
    • Impact: Since PCs and software are complements, lower PC prices increase demand for software ($D$ to $D^*$).
    • Big Picture: Software prices rise ($P_0$ to $P_1$); Quantity of software sold increases ($Q_0$ to $Q_1$).
    • Action Plan: Prepare for increased demand and higher price points.
• Conclusion on Comparative Statics:
  • Clarifies the "big picture" impact of events on equilibrium.
  • Provides a framework to organize action plans regarding production, inventories, and resources.