Economics, Choice, Production Possibilities Frontier (PPF), and Graphs

Scarcity, Tradeoffs, and Opportunity Cost

Economics is the study of how societies allocate limited resources to satisfy unlimited wants. Scarcity forces individuals and societies to make choices, leading to tradeoffs and opportunity costs.

• Scarcity: Limited resources versus unlimited wants.

• Tradeoff: Choosing more of one thing means having less of another.

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

• TANSTAAFL: "There Ain't No Such Thing As A Free Lunch"—all choices have costs.

• Microeconomics: Focuses on individuals and firms.

• Macroeconomics: Focuses on the overall economy.

Example: If you spend an hour studying economics instead of working for $15, your opportunity cost is $15.

Production Possibilities Frontier (PPF)

The PPF shows the maximum combinations of two goods that can be produced with available resources and technology.

• On the PPF: Efficient production (all resources fully used).

• Inside the PPF: Inefficient (resources underutilized).

• Outside the PPF: Unattainable with current resources.

• Moving along the PPF: Involves a tradeoff between goods.

• Straight-line PPF: Constant opportunity cost.

• Bowed-out PPF: Increasing opportunity cost.

• Shifts in the PPF: Caused by more resources or technological improvements.

Formula for Opportunity Cost from PPF:

• OC of X = Y given up / X gained

Example: Moving from 10 X & 20 Y to 15 X & 14 Y: Gain 5 X, give up 6 Y. OC of 1 X = 6/5 = 1.2 Y.

Comparative and Absolute Advantage

• Absolute Advantage (AA): Ability to produce more output with the same resources.

• Comparative Advantage (CA): Ability to produce at a lower opportunity cost.

Graphing and Slope

• Slope (m):

• Positive slope: As x increases, y increases.

• Negative slope: As x increases, y decreases.

• Steeper slope: Larger absolute value of slope.

• Horizontal slope: 0; Vertical slope: Undefined.

• x-axis: Independent/input variable; y-axis: Dependent/output variable.

Example: Points (2,4) and (6,12):

Economic Models and Marginal Analysis

Economic Models and Rational Decision-Making

Economic models assume rational decision-makers who respond to incentives and make choices at the margin.

• Marginal: Refers to the effect of one additional unit.

• Marginal Benefit (MB): Additional benefit from one more unit.

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

• Decision Rule: Undertake an action if ; do not if .

• Optimal Choice: Where for the last unit.

• Incentives: Changes in MB or MC alter choices.

• Demand Curve: Represents MB for consumers.

Example: Should you buy one more coffee? Compare the extra benefit (enjoyment) to the extra cost (price).

Demand, Supply, and Market Equilibrium

Law of Demand and Demand Shifters

• Law of Demand: As price (P) increases, quantity demanded (QD) decreases; as P decreases, QD increases.

• Movement along demand curve: Caused by a change in the good's own price.

• Shifts in demand: Caused by non-price factors:

  • Income (normal vs. inferior goods)

  • Prices of related goods (substitutes and complements)

  • Tastes and preferences

  • Expectations

  • Population/demographics

• Normal good: Income increases → demand increases.

• Inferior good: Income increases → demand decreases.

• Substitutes: Price of one increases → demand for the other increases.

• Complements: Price of one increases → demand for the other decreases.

Law of Supply and Supply Shifters

• Law of Supply: As price increases, quantity supplied (QS) increases; as price decreases, QS decreases.

• Movement along supply curve: Caused by a change in the good's own price.

• Shifts in supply: Caused by:

  • Input costs

  • Technology/process improvements

  • Number of firms

  • Expectations

  • Prices of related goods in production

Market Equilibrium

• Equilibrium: Where QD = QS; determines equilibrium price and quantity.

• Shortage: Price below equilibrium; QD > QS; upward pressure on price.

• Surplus: Price above equilibrium; QS > QD; downward pressure on price.

• Market-clearing price: The equilibrium price.

Effects of Shifts in Demand and Supply

• Demand increases: P↑, Q↑

• Demand decreases: P↓, Q↓

• Supply increases: P↓, Q↑

• Supply decreases: P↑, Q↓

• If both curves shift, analyze each effect separately; one variable may be ambiguous.

Exam Tip: First determine if a change is a movement along a curve (own price change) or a shift (other factors).

Welfare, Price Controls, and Taxes

Consumer and Producer Surplus

• Consumer Surplus (CS): Area between demand curve and price, up to quantity traded.

• Producer Surplus (PS): Area between price and supply curve, up to quantity traded.

• Total Welfare (W):

• Competitive Equilibrium: Maximizes total surplus; trades all units where .

Price Ceilings and Price Floors

• Price Ceiling: Legal maximum price.

  • Binding if below equilibrium → shortage; quantity traded = QS.

  • Nonbinding if above equilibrium → no effect.

  • Effects: shortages, black markets, lower quality, time/opportunity costs, deadweight loss (DWL).

• Price Floor: Legal minimum price.

  • Binding if above equilibrium → surplus; quantity traded = QD.

  • Nonbinding if below equilibrium → no effect.

  • Government may buy surplus under some systems.

Taxes and Deadweight Loss

• Excise Tax: Per-unit tax creates a wedge between price buyers pay and price sellers receive.

• Results: Q falls, CS↓, PS↓, government revenue↑, DWL↑.

• Tax Revenue:

• Tax Incidence: Who bears the burden depends on price changes, not legal assignment.

• Larger tax does not always mean larger revenue (Laffer curve concept).

• Deadweight Loss (DWL): Lost gains from trades that no longer occur due to the tax or policy.

Graph Analysis: Identify pre-policy equilibrium, post-policy quantity, CS/PS/revenue, and lost-surplus triangles (DWL).

International Trade and Trade Restrictions

Gains from Trade and Comparative Advantage

• Autarky: No international trade.

• Imports: Goods/services bought domestically but produced abroad.

• Exports: Domestic production sold abroad.

• Comparative Advantage: Lower opportunity cost in producing a good.

• Absolute Advantage: More output with the same resources.

• Specialize according to comparative advantage and trade to expand consumption possibilities.

Terms of Trade

• Terms of Trade: The rate at which one good is exchanged for another between countries.

• Mutually beneficial trade occurs at a price between the countries' opportunity costs.

• Complete specialization is rare due to non-tradable goods, rising opportunity costs, and differing preferences.

• Trade can benefit a country overall, but some groups may be hurt.

Trade Restrictions: Tariffs and Quotas

• Tariff: Tax on imports; raises domestic price, reduces imports, lowers consumer surplus, raises producer surplus, creates government revenue, and causes DWL.

• Quota: Numerical limit on imports; similar effects as tariffs, but quota rents may go to license holders.

• Both reduce total gains from trade and can create deadweight loss.

Trade Graph Analysis

• Identify world price, domestic consumption/production, and imports ().

• With a tariff, domestic price rises by the tariff amount (in the small-country model), imports fall, and CS/PS/revenue/DWL change.

• Use demand/supply and CS/PS framework for analysis.

Globalization and Trade Policy

• Globalization: Growth of international trade and economic integration.

• Trade Policy: Includes tariffs, quotas, and other restrictions; debates focus on gains from trade versus protectionism.

Fast Exam Method

1. Identify what changed.

2. Decide: movement along curve or shift?

3. Draw/trace the curve(s).

4. Find equilibrium or new quantity.

5. Apply the correct relationship/formula.

6. Check direction: P, Q, CS, PS, revenue, DWL.

7. For OC/CA: calculate OC first—lower OC = comparative advantage.