Microeconomics Foundations: Key Concepts, Models, and Market Dynamics

Introduction to Microeconomics

What is Economics?

Economics is the study of choices made by individuals, firms, and societies in the presence of limited resources. It examines how these agents allocate resources to satisfy their wants and needs.

• Scarcity: The fundamental economic problem where wants exceed available resources. Scarcity is not synonymous with poverty; it refers to the universal limitation of resources.

Microeconomics vs. Macroeconomics

• Microeconomics: Focuses on interactions between consumers and producers, firm decisions, competition, and individual market dynamics.

• Macroeconomics: Studies the economy as a whole, including government policy impacts and interactions between multiple economies.

• Examples:

  • Micro: Do flower shops sell more flowers on February 14th?

  • Micro: Do all Targets in America see increased sales around Christmas?

  • Macro: What is the GDP in America for 2025?

Introductory Economic Models

Five Foundations of Economics

These principles guide economic thinking and decision-making:

1. Incentives: Motivations that drive behavior, including positive (rewards) and negative (penalties).

2. Tradeoffs: Choosing one option means giving up others. Example: The cost of a bomber versus hospitals, power plants, or highways.

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

4. Marginal Thinking: Evaluating the benefit of one additional unit versus its cost.

5. Trade: Specialization and exchange make all parties better off.

Scientific Method in Economics

• Observe a phenomenon

• Develop a hypothesis

• Construct a model to test the hypothesis

• Design experiments to test the model

• Ceteris Paribus: Holding all other variables constant when testing one variable.

Model Variables

• Endogenous: Variables controlled or tested within the model.

• Exogenous: Variables outside the model, not controlled for but may affect outcomes.

Positive vs. Normative Statements

• Positive Statement: Testable and verifiable (fact-based).

• Normative Statement: Opinion-based, not testable or verifiable.

Supply and Demand

Opportunity Cost

The highest valued alternative forgone to engage in an activity or acquire a good.

• Formula: $Opportunity\ Cost = \frac{What\ you\ give\ up}{What\ you\ gain}$

Production Possibility Curve / Frontier (PPC/PPF)

The PPC/PPF illustrates the maximum output combinations of two goods that can be produced with fixed resources, assuming full and efficient use.

• Comparative Advantage: When an individual or entity can produce a good at a lower opportunity cost than another.

• Specialization and Trade: Entities should specialize in goods where they have comparative advantage and trade for others.

Law of Demand

There is an inverse relationship between the price of a good and the quantity demanded.

• As price increases, quantity demanded decreases.

• Change in Demand: Shift of the entire demand curve due to factors other than price or quantity demanded.

• Change in Quantity Demanded: Movement along the demand curve due to a change in price.

Law of Supply

There is a direct relationship between the price of a good and the quantity supplied.

• As price increases, quantity supplied increases.

• Change in Supply: Shift of the entire supply curve due to factors other than price or quantity supplied.

• Change in Quantity Supplied: Movement along the supply curve due to a change in price.

Market Equilibrium

The point where quantity demanded equals quantity supplied. The market naturally moves toward equilibrium, guided by the 'Invisible Hand' (Adam Smith).

Elasticity

Definition and Types

Elasticity measures the percentage change in one variable relative to a percentage change in another variable.

• Elastic: Quantity demanded changes by a greater percentage than price (ED < -1).

• Inelastic: Quantity demanded changes by a smaller percentage than price (ED > -1).

Calculating Elasticity

• General Formula: $E = \frac{\%\ change\ in\ X}{\%\ change\ in\ Y}$

• Percentage Change Formula: $\frac{x_2 - x_1}{x_1} \times 100$

Price Elasticity of Demand

• Formula: $ED = \frac{\%\ change\ in\ QD}{\%\ change\ in\ P}$

• Always negative due to the inverse relationship.

Income Elasticity of Demand

• Formula: $EI = \frac{\%\ change\ in\ QD}{\%\ change\ in\ I}$

• Inferior Goods: EI < 0

• Normal Goods: EI > 0

• Necessity: $0 < EI < 1$

• Luxury: $EI > 1$

Cross-Price Elasticity of Demand

• Formula: $EC = \frac{\%\ change\ in\ QD\ of\ good\ A}{\%\ change\ in\ P\ of\ good\ B}$

• EC > 0: Substitutes

• EC < 0: Complements

Price Elasticity of Supply

• Formula: $ES = \frac{\%\ change\ in\ QS}{\%\ change\ in\ P}$

• ES = 0: Perfectly Inelastic

• 0 < ES < 1: Relatively Inelastic

• ES > 1: Relatively Elastic

• ES = 1: Unitary Elasticity

• Perfectly elastic supply does not exist due to scarcity.

Consumer and Producer Surplus; Price Ceilings and Price Floors

Consumer Surplus

The difference between what consumers are willing to pay and what they actually pay for a good.

Producer Surplus

The difference between the price sellers receive and the minimum price they are willing to accept.

Total Surplus and Efficiency

• Total Surplus: $CS + PS$

• Efficiency: Allocation of resources that maximizes total surplus.

Taxes and Deadweight Loss

• Levy: Who is legally responsible for paying a tax.

• Incidence: Who actually bears the economic burden of the tax.

• Deadweight Loss: Loss in economic activity and surplus due to inefficiency.

• Main Incentives: Taxes reduce economic activity and raise government revenue.

• Consumer Incidence: Portion of tax paid by consumers.

• Producer Incidence: Portion of tax paid by producers.

Price Ceilings and Price Floors

• Price Ceiling: Legally imposed maximum price for a good.

• Price Floor: Legally imposed minimum price for a good.

• Binding: Restricts market equilibrium, causing shortages (ceiling) or surpluses (floor).

• Non-binding: No effect on market equilibrium.

• Price Gouging: Raising prices during emergencies; often illegal after a declared state of emergency.

Summary Table: Types of Elasticity

Type	Formula	Interpretation
Price Elasticity of Demand	$ED = \frac{\%\ change\ in\ QD}{\%\ change\ in\ P}$	How QD responds to price changes; negative value
Income Elasticity of Demand	$EI = \frac{\%\ change\ in\ QD}{\%\ change\ in\ I}$	How QD responds to income changes; positive or negative
Cross-Price Elasticity of Demand	$EC = \frac{\%\ change\ in\ QD\ of\ A}{\%\ change\ in\ P\ of\ B}$	How QD of one good responds to price changes of another; positive (substitutes), negative (complements)
Price Elasticity of Supply	$ES = \frac{\%\ change\ in\ QS}{\%\ change\ in\ P}$	How QS responds to price changes; always positive

Additional info: Academic context and definitions have been expanded for clarity and completeness. Examples and formulas are provided for exam preparation.