Microeconomics: Core Concepts and Principles – Study Notes

Module 1: Introduction to Microeconomics

What is Economics?

• Economics: The study of choices people make as they try to attain their goals, given their scarce resources.

• Economic Models: Simplified frameworks for understanding complex economic processes.

• Scarcity: A situation in which unlimited wants exceed the limited resources available to fulfill those wants.

Microeconomics vs. Macroeconomics

• Microeconomics: Study of individual units, such as households and firms, and how they make choices.

• Macroeconomics: Study of the economy as a whole, including topics like inflation, unemployment, and economic growth.

Three Key Economic Ideas

• People are rational: Individuals use all available information to achieve their goals.

• People respond to incentives: Incentives affect the actions of individuals and firms.

• Optimal decisions are made at the margin: Most decisions involve doing a little more or a little less of something.

Economic Problem for Society

• Trade-offs: Producing more of one good or service means producing less of another due to scarcity.

• Opportunity Cost: The highest-valued alternative that must be given up to engage in an activity.

Types of Economies

• Centrally planned economy: Government decides how resources are allocated.

• Market economy: Decisions of households and firms interacting in markets allocate resources.

• Mixed economy: Features of both centrally planned and market economies.

Efficiency in the Economy

• Productive efficiency: Goods and services are produced at the lowest possible cost.

• Allocative efficiency: Production is consistent with consumer preferences; every good or service is produced up to the point where the last unit provides a marginal benefit to society equal to the marginal cost of producing it.

Economic Models and Causation

• Models help economists analyze real-world issues and make predictions.

• Causation vs. Correlation: Correlation does not imply causation.

Formulas

• Percentage Change: $\text{Percentage Change} = \frac{\text{Value in the second period} - \text{Value in the first period}}{\text{Value in the first period}} \times 100$

• Area of a Rectangle: $\text{Area} = \text{Height} \times \text{Width}$

• Area of a Triangle: $\text{Area} = \frac{1}{2} \times \text{Base} \times \text{Height}$

Module 2: Trade-offs and the Production Possibility Frontier (PPF)

Trade-offs

• Households, firms, and governments must decide how to best use scarce resources.

• Economics teaches us how to make good trade-offs.

Production Possibility Frontier (PPF)

• A curve showing the maximum attainable combinations of two products that may be produced with available resources and current technology.

• Points inside the PPF are inefficient, points on the PPF are efficient, and points outside are unattainable.

Opportunity Cost and Slope

• The opportunity cost of producing more of one good is the amount of the other good that must be given up.

• The slope of the PPF represents the opportunity cost.

Economic Growth and Technological Change

• Economic growth shifts the PPF outward, allowing more of both goods to be produced.

• Technological change in one industry rotates the PPF outward for that good.

Comparative and Absolute Advantage

• Comparative advantage: The ability to produce a good at a lower opportunity cost than another producer.

• Absolute advantage: The ability to produce more of a good with the same resources than another producer.

Table: Comparative Advantage Example

	Apple O.C.	Cherry O.C.
You	1 Cherry	1 Apple
Neighbor	2 Cherries	1/2 Apple

• Comparative advantage: You specialize in apples (lower opportunity cost), neighbor specializes in cherries.

Market Economy and Circular Flow Diagram

• Households own factors of production and sell them to firms for income.

• Firms buy factors of production and use them to produce goods and services.

• The circular flow diagram illustrates the flow of resources and products in the economy.

Module 3: Supply and Demand

Demand

• Law of Demand: Holding everything else constant, when the price of a product falls, the quantity demanded increases, and when the price rises, the quantity demanded decreases.

• Market Demand Curve: The sum of the individual demand curves of all potential buyers.

• Factors that shift demand: income, prices of related goods, tastes, population and demographics, expectations.

Supply

• Law of Supply: Holding everything else constant, increases in price cause increases in the quantity supplied, and decreases in price cause decreases in the quantity supplied.

• Factors that shift supply: prices of inputs, technological change, prices of substitutes in production, number of firms, expected future prices.

Market Equilibrium

• The point where quantity demanded equals quantity supplied.

• Competitive market equilibrium: Many buyers and sellers, no single buyer or seller can influence the price.

Shifts in Demand and Supply

• Increase in demand shifts the demand curve right; decrease shifts it left.

• Increase in supply shifts the supply curve right; decrease shifts it left.

• Simultaneous shifts affect equilibrium price and quantity depending on the magnitude of each shift.

Module 4: Consumer and Producer Surplus

Consumer Surplus

• The difference between the highest price a consumer is willing to pay and the price the consumer actually pays.

Producer Surplus

• The difference between the lowest price a firm would accept for a good or service and the price it actually receives.

Economic Efficiency

• Occurs when the sum of consumer and producer surplus is maximized.

• Deadweight loss: The reduction in economic surplus resulting from a market not being in competitive equilibrium.

Government Intervention

• Price controls (ceilings and floors) and taxes can lead to inefficiency and deadweight loss.

• Tax incidence: The division of the burden of a tax between buyers and sellers, determined by the relative slopes of the demand and supply curves.

Module 5: Elasticity

Price Elasticity of Demand

• Measures how much the quantity demanded changes when the price changes.

• Midpoint formula: $\text{Price Elasticity of Demand} = \frac{\frac{Q_2 - Q_1}{(Q_2 + Q_1)/2}}{\frac{P_2 - P_1}{(P_2 + P_1)/2}}$

• Elasticity classifications:

  • Elastic: $E_d > 1$

  • Inelastic: $E_d < 1$

  • Unit elastic: $E_d = 1$

Determinants of Elasticity

• Availability of close substitutes

• Passage of time

• Necessities vs. luxuries

• Definition of the market

• Share of a good in a consumer’s budget

Other Elasticities

• Cross-price elasticity of demand: Measures the responsiveness of quantity demanded of one good to a change in the price of another good.

• Income elasticity of demand: Measures the responsiveness of quantity demanded to changes in income.

• Price elasticity of supply: Measures the responsiveness of quantity supplied to changes in price.

Module 6: Production and Costs

Production Function

• Shows the relationship between inputs and maximum output.

• Marginal Product of Labor (MPL): $\text{MPL} = \frac{\Delta Q}{\Delta L}$

• Average Product of Labor (APL): $\text{APL} = \frac{\text{Total Output}}{\text{Number of Workers}}$

Costs

• Fixed costs (FC): Costs that remain constant as output changes.

• Variable costs (VC): Costs that change as output changes.

• Total cost (TC): $\text{TC} = \text{FC} + \text{VC}$

• Average total cost (ATC): $\text{ATC} = \frac{\text{TC}}{Q}$

• Marginal cost (MC): $\text{MC} = \frac{\Delta \text{TC}}{\Delta Q}$

Short Run vs. Long Run

• Short run: At least one input is fixed.

• Long run: All inputs are variable.

Economies and Diseconomies of Scale

• Economies of scale: ATC falls as output increases.

• Diseconomies of scale: ATC rises as output increases.

Module 7: Market Structures

Perfect Competition

• Many buyers and sellers, identical products, no barriers to entry.

• Firms are price takers.

• Profit maximization: Produce where $MR = MC$.

• In the long run, firms earn zero economic profit due to entry and exit.

Monopoly

• Single seller, unique product, high barriers to entry.

• Monopolist sets price and output to maximize profit ($MR = MC$).

• Results in higher prices and lower output compared to perfect competition.

Monopolistic Competition

• Many firms, differentiated products, free entry and exit.

• Firms have some market power due to product differentiation.

• In the long run, firms earn zero economic profit.

Oligopoly

• Few firms, products may be identical or differentiated, barriers to entry.

• Firms are interdependent; strategic behavior is important (game theory).

Game Theory in Oligopoly

• Analyzes strategic interactions among firms.

• Includes concepts like Nash equilibrium, collusion, and cartels (e.g., OPEC).

Market Concentration

• Measured by concentration ratios and the Herfindahl-Hirschman Index (HHI).

• Higher concentration indicates less competition.

Additional info:

• These notes cover core microeconomic concepts from introductory chapters, including supply and demand, elasticity, production and costs, and market structures. They are suitable for exam preparation and foundational understanding in a college-level microeconomics course.