CFA Level I: Economics — Demand, Supply and Market Structures

TL;DR

You'll learn how demand and supply interact to determine prices and quantities in different market structures. Understanding these forces helps you analyze how various factors impact economic outcomes. We'll explore perfect competition, monopolistic competition, oligopoly, and monopoly, highlighting their key characteristics.

1. The Mental Model

Think of markets as a constant tug-of-war between buyers (demand) wanting lower prices and sellers (supply) wanting higher prices. The market structure dictates the rules of this tug-of-war, influencing prices, profits, and how much is produced.

2. The Core Material

Demand and Supply Fundamentals

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Demand represents the quantity of a good or service consumers are willing and able to buy at various prices, holding all other factors constant. The Law of Demand states that as price increases, quantity demanded decreases (inverse relationship).

Supply represents the quantity of a good or service producers are willing and able to sell at various prices, holding all other factors constant. The Law of Supply states that as price increases, quantity supplied increases (direct relationship).

The point where quantity demanded equals quantity supplied is the equilibrium price and quantity. At this point, there's no pressure for prices to change.

Factors that shift the demand curve (change in demand) include:
* Consumer income
* Tastes and preferences
* Prices of related goods (substitutes, complements)
* Consumer expectations
* Population size

Factors that shift the supply curve (change in supply) include:
* Input prices (cost of production)
* Technology
* Government taxes or subsidies
* Producer expectations
* Number of sellers

Elasticity

Elasticity measures the responsiveness of one variable to a change in another.

• Price Elasticity of Demand (PED): Measures how much quantity demanded changes in response to a price change.
  • If PED > 1, demand is elastic (responsive).
  • If PED < 1, demand is inelastic (unresponsive).
  • If PED = 1, demand is unit elastic.
• Price Elasticity of Supply (PES): Measures how much quantity supplied changes in response to a price change.
• Income Elasticity of Demand (IED): Measures how much quantity demanded changes in response to an income change.
  • Positive IED: Normal good.
  • Negative IED: Inferior good.
• Cross-Price Elasticity of Demand (CPED): Measures how much quantity demanded of good A changes in response to a price change of good B.
  • Positive CPED: Substitutes.
  • Negative CPED: Complements.

Market Structures

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Market structures are categorized based on factors like the number of firms, product differentiation, barriers to entry, and pricing power.

graph TD
    A["Market Structures"] --> B["Perfect Competition"]
    A --> C["Monopolistic Competition"]
    A --> D["Oligopoly"]
    A --> E["Monopoly"]

    B --> B1["Many small firms"]
    B --> B2["Homogeneous product"]
    B --> B3["No barriers to entry/exit"]
    B --> B4["Price takers"]
    B --> B5["Zero economic profit (long-run)"]

    C --> C1["Many firms"]
    C --> C2["Differentiated product"]
    C --> C3["Low barriers to entry/exit"]
    C --> C4["Some pricing power"]
    C --> C5["Zero economic profit (long-run)"]

    D --> D1["Few large firms"]
    D --> D2["Homogeneous or differentiated product"]
    D --> D3["High barriers to entry"]
    D --> D4["Interdependent pricing"]
    D --> D5["Potential for positive economic profit (long-run)"]

    E --> E1["Single firm"]
    E --> E2["Unique product"]
    E --> E3["Very high barriers to entry"]
    E --> E4["Significant pricing power"]
    E --> E5["Potential for positive economic profit (long-run)"]

• Perfect Competition: Many small firms, identical products, no barriers to entry. Firms are price takers. In the long run, economic profit is zero.
• Monopolistic Competition: Many firms, differentiated products, low barriers to entry. Firms have some pricing power. In the long run, economic profit is zero.
• Oligopoly: Few large firms, products can be identical or differentiated, high barriers to entry. Firms are interdependent; one firm's actions significantly affect others. Can lead to collusion or price wars.
• Monopoly: A single firm, unique product, very high barriers to entry. The firm has significant pricing power. Can earn positive economic profits in the long run.

3. Worked Example

Let's say the government imposes a new tax on producers of a popular snack food.

1. Initial State: The market is in equilibrium with a price (P1) and quantity (Q1).
2. Impact of Tax: The tax increases the cost of production for each unit. This means producers are now willing to supply less at every given price, or equivalently, they need a higher price to supply the same quantity.
3. Supply Curve Shift: The supply curve shifts to the left (or upwards).
4. New Equilibrium: The leftward shift of the supply curve, with no change in demand, leads to a new equilibrium. The new equilibrium price (P2) will be higher than P1, and the new equilibrium quantity (Q2) will be lower than Q1.
5. Conclusion: A tax on producers generally leads to higher prices for consumers and a lower quantity of goods sold in the market.

4. Key Takeaways

• Demand and supply curves intersect at the equilibrium price and quantity, where the market clears.
• Shifts in demand or supply curves are caused by factors other than the good's own price.
• Elasticity measures the responsiveness of quantity to changes in price, income, or the price of related goods.
• Perfect competition features many small firms and homogeneous products, leading to zero long-run economic profit.
• Monopolistic competition involves many firms selling differentiated products, also leading to zero long-run economic profit.
• Oligopoly is characterized by a few large interdependent firms with high barriers to entry.
• Monopoly is a single firm with significant market power and very high barriers to entry.

Common Mistakes:
- Confusing a "change in quantity demanded/supplied" (movement along the curve due to price) with a "change in demand/supply" (shift of the entire curve due to other factors).
- Misinterpreting elasticity values (e.g., thinking a PED of 0.5 means demand is highly responsive).
- Assuming all market structures always earn positive economic profit.
- Forgetting that "economic profit" accounts for opportunity costs, unlike "accounting profit."

5. Now Try It

For 15 minutes, draw a simple demand and supply graph. Then, consider two scenarios:
1. A popular celebrity endorses a new brand of running shoes. Show how this impacts the market for these shoes.
2. A technological breakthrough significantly reduces the cost of producing solar panels. Show how this impacts the market for solar panels.

For each scenario, identify which curve shifts, in which direction, and what happens to the equilibrium price and quantity. Success looks like clearly drawn graphs with correctly labeled shifts and accurate descriptions of the resulting changes in price and quantity for both scenarios.