Economics: Foundations and Models

Three Key Economic Ideas

Economics is built on several foundational assumptions about individual and market behavior.

• Rationality: Individuals make decisions by comparing costs and benefits, aiming to maximize their well-being.

• Response to Incentives: Changes in costs or benefits lead to changes in behavior. For example, higher prices typically reduce quantity demanded, while higher wages increase labor supply.

Scarcity and Trade-Offs

Scarcity means resources are limited, but human wants are unlimited, necessitating choices and trade-offs.

• Scarcity: The fundamental economic problem of having limited resources to meet unlimited wants.

• Trade-Offs: Choosing one option means giving up another due to scarcity. This applies to all individuals, regardless of income.

• Opportunity Cost: The value of the next best alternative forgone when making a choice.

Trade-Offs and Comparative Advantage

Production Possibilities Frontier (PPF)

The PPF illustrates the maximum feasible combinations of two goods that an economy can produce with available resources and technology.

• Efficient Points: On the PPF curve; all resources are fully utilized.

• Inefficient Points: Inside the PPF; resources are underutilized.

• Unattainable Points: Outside the PPF; not possible with current resources.

• Opportunity Cost: Moving along the PPF shows what must be given up to produce more of another good. A bowed-outward PPF indicates increasing opportunity costs.

• Economic Growth: Outward shifts of the PPF represent growth, allowing more of both goods to be produced.

Comparative Advantage

Comparative advantage is the ability to produce a good at a lower opportunity cost than others.

• Absolute Advantage: The ability to produce more of a good with the same resources.

• Gains from Trade: Specialization based on comparative advantage allows all parties to benefit, even if one has an absolute advantage in all goods.

Demand and Supply

Market Equilibrium

Market equilibrium occurs where quantity demanded equals quantity supplied.

• Shortage: Price below equilibrium; quantity demanded exceeds quantity supplied, causing upward pressure on price.

• Surplus: Price above equilibrium; quantity supplied exceeds quantity demanded, causing downward pressure on price.

• Equilibrium: No surplus or shortage; market clears.

Shifts in Demand and Supply

It is crucial to distinguish between movements along a curve and shifts of the curve.

• Movement Along Curve: Caused by price changes.

• Shift of Curve: Caused by external factors (e.g., income, tastes, technology).

• Double Shifters: When both demand and supply shift, the effect on price and quantity depends on the magnitude and direction of each shift.

• Key Relationships:

  • If both price and quantity decrease, demand has decreased.

  • If price decreases and quantity increases, supply has increased.

Efficiency, Price Controls, and Taxes

Consumer and Producer Surplus

Surplus measures the benefit to buyers and sellers from market transactions.

• Consumer Surplus: The difference between what consumers are willing to pay and what they actually pay.

• Producer Surplus: The difference between the price received and the cost of production.

Economic Efficiency

An outcome is efficient when marginal benefit equals marginal cost.

• If output is below this level, marginal benefit exceeds marginal cost, indicating more should be produced.

• If price is above equilibrium, marginal benefit exceeds marginal cost and vice versa.

Price Controls

• Price Ceiling: A legal maximum price (e.g., rent control) leads to shortages.

• Price Floor: A legal minimum price leads to surpluses.

• Identify who benefits (e.g., consumers under a ceiling) and who is harmed (e.g., producers under a ceiling).

Taxes

Taxes create a wedge between the price buyers pay and the price sellers receive.

• Buyers pay more; sellers receive less (net of tax).

• The burden of a tax (tax incidence) falls more on the side of the market that is less elastic (less responsive to price changes).

Externalities and Public Goods

Externalities

Externalities occur when a third party is affected by a transaction.

• Negative Externalities: Lead to overproduction (e.g., pollution).

• Positive Externalities: Lead to underproduction (e.g., education).

Private Solutions and Government Policy

• Coase Theorem: Private negotiations can resolve externalities if property rights are well-defined and transaction costs are low.

• Command-and-Control Policies: Direct regulation (e.g., pollution limits).

• Market-Based Policies: Taxes or subsidies to create incentives (e.g., carbon tax).

Four Categories of Goods

Goods are classified by rivalry and excludability:

• Common resources can be overused ("tragedy of the commons").

Elasticity

Price Elasticity of Demand

Elasticity measures how responsive quantity demanded is to price changes.

• Elastic Demand: Quantity demanded changes significantly with price changes.

• Inelastic Demand: Quantity demanded changes little with price changes.

• Perfectly Inelastic: Vertical demand curve; .

• Perfectly Elastic: Horizontal demand curve; .

• Formula:

• Example: If , a 1% increase in price causes a 0.8% decrease in quantity demanded.

Determinants of Elasticity

• Availability of close substitutes (more substitutes = more elastic demand).

• Narrowly defined markets are more elastic (e.g., Starbucks vs. coffee).

• Longer time horizons increase elasticity (demand is more elastic in the long run).

Elasticity and Revenue

• If demand is elastic (), increasing price decreases total revenue.

• If demand is inelastic (), increasing price increases total revenue.

• Firms can estimate elasticity by observing how total revenue changes with price.

Price Elasticity of Supply

• Measures how responsive quantity supplied is to price changes.

• Supply is generally more elastic in the long run.

International Trade

Trade and Tariffs

• Tariff: A tax on imports; raises prices and reduces trade.

Gains from Trade

• Trade allows countries to specialize based on comparative advantage.

• Results in lower prices, greater variety, and increased welfare.

• Mutually beneficial trade is possible even if one country has an absolute advantage in all goods.

Production and Costs

Positive Technological Change

• Occurs when a firm can produce more output with the same inputs.

Production and Diminishing Returns

• Adding more of a variable input (e.g., labor) increases output, but at a decreasing rate (law of diminishing marginal returns).

• This explains why average total cost (ATC) and marginal cost (MC) curves are U-shaped in the short run.

Cost Concepts

• Marginal Cost (MC): Additional cost of producing one more unit.

• Average Total Cost (ATC): Total cost divided by output.

• Average Variable Cost (AVC): Variable cost divided by output.

• Average Fixed Cost (AFC): Fixed cost divided by output.

• The MC curve intersects the ATC and AVC curves at their minimum points.

Long Run Costs

• All inputs are variable; firms can adjust scale to minimize costs.

• The long run average cost (LRAC) curve shows the lowest average cost for each output level.

Perfect Competition

Market Structure

• Many buyers and sellers.

• Identical products.

• No barriers to entry.

Profit Maximization

• Firms maximize profit where marginal revenue equals marginal cost ().

Shutdown Decision

• A firm should shut down in the short run if price is less than average variable cost ().

Long Run Equilibrium

• Firms earn zero economic profit in the long run (break even).

• Price equals minimum average total cost ().

Monopolistic Competition

Key Features

• Many firms.

• Differentiated products.

• Some control over price.

• Low barriers to entry.

Firm Behavior

• Downward-sloping demand curve; must lower price to sell more.

• Maximize profit where marginal revenue equals marginal cost ().

Long Run Outcome

• Entry of new firms eliminates profits; zero economic profit in the long run.

Consumer Benefits

• Greater product variety; products more closely match consumer preferences.

Oligopoly

Market Characteristics

• Few firms dominate the market.

• Firms are interdependent; one firm's decisions affect others.

Game Theory

• Dominant Strategy: The best strategy for a firm, regardless of what others do.

• Firms must anticipate competitors' responses when making decisions.

Monopoly

Barriers to Entry

• High (insurmountable) barriers are necessary to maintain monopoly power.

Pricing and Output

• The monopolist's demand curve is the market demand curve.

• Must lower price to sell additional units.

Profit Maximization

• Produce where marginal revenue equals marginal cost ().

• Charge the corresponding price on the demand curve.

• Profit-maximizing price exceeds marginal cost.

Efficiency

• Monopolies are inefficient: price exceeds marginal cost, creating deadweight loss.

Final Exam Strategy

• Be able to interpret graphs (cost curves, demand and supply, market structures).

• Understand key decision rules (e.g., ).

• Apply economic reasoning, not just memorization.

• Distinguish between similar concepts (e.g., shifts vs. movements, elasticity vs. slope).