Essential Microeconomics Principles and Market Models
Chapter 1: Ten Principles of Economics
How People Make Decisions
1. People Face Trade-offs
Scarcity forces choices. Examples include:
- Efficiency vs. equality
- Work vs. leisure
- Clean environment vs. economic output
2. The Cost of Something Is What You Give Up to Get It
Opportunity cost is the next-best alternative. Examples include:
- College = tuition + books + forgone wages
- Watching a movie = ticket price + lost study time
3. Rational People Think at the Margin
Rational agents compare:
- Marginal Benefit (MB)
- Marginal Cost (MC)
Decisions are made where MB ≥ MC.
4. People Respond to Incentives
Incentives change behavior. Examples include:
- Higher cigarette taxes lead to fewer smokers.
- Seat belts make driving safer but can lead to riskier driving (offsetting behavior).
How People Interact
5. Trade Can Make Everyone Better Off
- Allows for specialization.
- Increases total production and variety.
Trade benefits both sides even if one is more productive in everything.
6. Markets Organize Economic Activity
The “invisible hand” uses prices to guide economic decision-makers. Markets coordinate millions of individuals without the need for central planning.
7. Governments Can Sometimes Improve Market Outcomes
Reasons for intervention:
- Enforce property rights.
- Correct market failures (externalities, monopoly power).
- Improve equity via redistribution.
How the Economy as a Whole Works
8. Living Standards Depend on Productivity
Productivity is the output per worker. Main determinants include:
- Technology
- Human capital
- Physical capital
- Institutions
9. Prices Rise When Government Prints Too Much Money
Excessive money supply leads to inflation. In the long run, prices are tied directly to the money supply.
10. Inflation and Unemployment Trade-off
In the short run, increasing the money supply leads to higher output and lower unemployment, as illustrated by the Phillips Curve.
Chapter 2: Thinking Like an Economist
Economists as Scientists
- Use the scientific method.
- Build models to simplify reality.
- Use natural experiments and data.
Assumptions
Economists simplify the world to highlight key mechanisms. Examples include:
- The perfect competition assumption.
- Rationality.
- Holding other variables constant (ceteris paribus).
Economic Models
Circular Flow Diagram
Shows interactions between households and firms across two markets:
- Goods and services
- Factors of production (labor, land, capital)
Money flows in one direction, while resources and products flow in the other.
Production Possibilities Frontier (PPF)
A graph showing combinations of two goods an economy can produce. Key concepts include:
- Points on the curve are efficient.
- Points inside the curve are inefficient.
- Points outside the curve are unattainable without trade.
- A bowed-out shape indicates increasing opportunity costs.
Positive vs. Normative Analysis
- Positive statements are objective and describe what “is.”
- Normative statements are prescriptive and describe what “should be.”
Why Economists Disagree
- Differences in scientific judgments.
- Differences in values.
- Different assumptions or data limitations.
Chapter 3: Interdependence and Gains from Trade
Absolute Advantage
The ability to produce a good using fewer inputs than another producer.
Comparative Advantage
The ability to produce a good at a lower opportunity cost. This determines who should specialize in specific tasks.
Law of Comparative Advantage
Each person or country should produce the good for which they have the lower opportunity cost.
Opportunity Cost Calculation
If Ruby takes 20 minutes to make meat and 10 minutes for potatoes:
- OC(meat) = 20/10 = 2 potatoes.
Gains from Trade
- Specialization expands consumption possibilities.
- Total output increases.
- The trade price must lie between both producers’ opportunity costs.
Applications
- International trade (e.g., U.S. cars vs. Japanese food).
- Should Serena Williams mow her own lawn? No, because she has a high opportunity cost.
Chapter 4: Supply and Demand
Demand
Law of Demand: As Price ↑, Quantity Demanded ↓. Shifters include:
- Income and tastes.
- Prices of related goods (substitutes/complements).
- Expectations and the number of buyers.
Supply
Law of Supply: As Price ↑, Quantity Supplied ↑. Shifters include:
- Input prices and technology.
- Expectations and the number of sellers.
Market Equilibrium
Occurs where Qd = Qs. In disequilibrium:
- Surplus: Price is above equilibrium.
- Shortage: Price is below equilibrium.
Shifts vs. Movement Along the Curve
- A change in price causes movement along the curve.
- A change in any shifter causes the curve to shift.
Chapter 5: Elasticity
Price Elasticity of Demand
Measures responsiveness to price changes. Formula: (%ΔQ / %ΔP).
Elasticity Values
- > 1: Elastic
- < 1: Inelastic
- = 1: Unit elastic
- 0: Perfectly inelastic
- ∞: Perfectly elastic
Determinants of Elasticity
- Availability of substitutes.
- Necessity vs. luxury.
- Definition of the market and time horizon.
Elasticity and Total Revenue (TR)
- If demand is elastic: Price ↑ leads to TR ↓.
- If demand is inelastic: Price ↑ leads to TR ↑.
Cross-Price and Income Elasticity
- Substitutes: Positive cross-price elasticity.
- Complements: Negative cross-price elasticity.
- Normal goods: Positive income elasticity.
- Inferior goods: Negative income elasticity.
Chapter 6: Supply, Demand, and Government Policies
Price Ceilings
Binding if set below equilibrium. Effects include:
- Shortages and black markets.
- Lower quality and reduced long-run supply (e.g., rent control).
Price Floors
Binding if set above equilibrium. Effects include:
- Surpluses and unemployment (e.g., minimum wage).
- Waste of resources.
Taxes and Tax Incidence
Taxes drive a wedge between the price paid by buyers and the price received by sellers. Tax incidence (who bears the burden) depends on elasticity:
- The more elastic side bears less of the burden.
- The less elastic side bears more of the burden.
Chapter 7: Consumers, Producers, and Market Efficiency
Consumer and Producer Surplus
- Consumer Surplus: Area below the demand curve and above the price.
- Producer Surplus: Area above the supply curve and below the price.
- Total Surplus: CS + PS (maximized in competitive equilibrium).
Efficiency and the Invisible Hand
Markets allocate goods to buyers who value them most and sellers who can produce at the lowest cost. Market failure occurs when externalities or market power are present.
Chapter 8: Costs of Taxation
Deadweight Loss (DWL)
The lost total surplus resulting from a reduced quantity of trade. DWL is larger for elastic supply/demand and grows more than proportionally with tax size.
Tax Revenue and the Laffer Curve
Tax Revenue = T × Q. The Laffer Curve shows that higher tax rates may eventually reduce total revenue by shrinking the market significantly.
Chapter 10: Externalities
Negative Externalities
Examples include pollution and second-hand smoke. Social cost > private cost, leading to market output that is too high. Solutions include:
- Corrective (Pigovian) taxes.
- Regulation and tradable permits.
Positive Externalities
Examples include education and vaccines. Social value > private value, leading to market output that is too low. Solutions include subsidies and government provision.
Coase Theorem
If property rights are well-defined and transaction costs are low, private bargaining will lead to an efficient outcome.
Chapter 11: Public Goods and Common Resources
Public Goods
Non-rival and non-excludable (e.g., national defense). The primary problem is free-riding, which often requires government provision.
Common Resources
Rival but non-excludable (e.g., clean air, fisheries). The primary problem is the Tragedy of the Commons. Solutions include regulation, quotas, and property rights.
Chapter 14: The Costs of Production
Total Cost (TC)
Includes both explicit and implicit costs. The production function shows the relationship between input and output, often exhibiting diminishing marginal product.
Cost Curves
- MC rises due to diminishing returns.
- ATC = AFC + AVC.
- MC intersects ATC at its minimum point.
Short Run vs. Long Run
- Short Run: Some costs are fixed.
- Long Run: All costs are variable; firms can enter or exit.
- Economies of Scale: ATC falls as Q increases.
- Diseconomies of Scale: ATC rises as Q increases due to coordination problems.
Chapter 15: Monopoly
Characteristics and Power
A single seller with no close substitutes and high barriers to entry. Sources of power include resource ownership, government regulation (patents), and natural monopolies.
Profit Maximization
Monopolists face a downward-sloping market demand curve where MR < Price. They maximize profit where MR = MC and charge the corresponding price from the demand curve.
Market Inefficiency
Because P > MC, a deadweight loss exists. Monopolists produce less than the socially optimal competitive output.
Price Discrimination
Charging different prices to different consumers (e.g., perfect, group, or versioning). This can eliminate DWL and transfer surplus to the producer.
Chapter 16: Oligopoly
Characteristics
A market with few sellers and interdependent decisions. Firms may attempt collusion or form cartels to act like a monopoly, though this is often illegal.
Game Theory and Equilibrium
- Nash Equilibrium: Each player chooses the best strategy given others’ strategies.
- Prisoner’s Dilemma: Illustrates why cooperation is difficult even when it is mutually beneficial.
Output Strategies
- Cournot: Firms choose quantities; output is between monopoly and competitive levels.
- Bertrand: Firms choose prices; identical products lead to P = MC.
Chapter 18: Competitive and Factor Markets
Note: This section includes long-run competitive firm behavior from later chapters of Mankiw.
Competitive Firm Characteristics
- Firms are price takers.
- P = MR = AR.
- The demand curve for an individual firm is horizontal.
Profit Maximization and Decisions
Produce where P = MC.
- Shutdown (Short Run): If P < AVC.
- Exit (Long Run): If P < ATC.
Long-Run Equilibrium
Firms earn zero economic profit where Price = minimum ATC. Entry and exit adjust market supply until profits are neutralized. In the short run, demand shifts cause price jumps and profits/losses; in the long run, supply shifts return the price to the minimum ATC.