Microeconomics: Principles, Methods, and Consumer Behavior – Study Notes

Chapter 1. The Principle and Practice of Economics

1.1 The Scope of Economics

Economics studies how individuals and societies allocate scarce resources to satisfy unlimited wants. It involves understanding the behavior of economic agents and the use of economic resources.

• Economic agents: Individuals or groups making choices (e.g., consumers, firms, governments).

• Economic resources: Inputs used to produce goods and services (land, labor, capital, entrepreneurship).

• What is Economics: The study of scarcity, choice, and opportunity cost.

• Positive vs. Normative Economics: Positive economics describes and predicts economic phenomena; Normative economics prescribes policies or outcomes based on value judgments.

• Microeconomics vs. Macroeconomics: Microeconomics focuses on individual markets and agents; Macroeconomics studies the economy as a whole.

1.2 The Principles of Economics

Core principles guide economic thinking and decision-making.

• Optimization: Making the best possible choice given constraints.

• Trade-offs: Choosing one thing often means giving up something else.

• Budget constraints: The limits imposed by income and prices.

• Opportunity cost: The value of the next best alternative forgone.

• Cost-benefit analysis: Comparing the costs and benefits of an action.

1.4 Equilibrium

Markets tend toward a state where no individual has an incentive to change their behavior.

• The free rider problem: When individuals benefit from resources without paying for them.

1.5 Empiricism

Empiricism involves using data and evidence to test economic theories and inform decisions.

Chapter 2. Economic Methods and Economic Questions

2.1 The Scientific Method

Economists use models and data to analyze economic questions.

• Models and data: Simplified representations of reality to predict outcomes.

• Economic models: Theoretical frameworks for understanding economic processes.

• The mean and the median: Measures of central tendency in data.

2.2 Causation and Correlation

Understanding the difference between correlation and causation is crucial in economics.

• Positive and negative correlation: Variables move together or in opposite directions.

• Omitted variables bias: When a model leaves out a relevant variable, leading to incorrect conclusions.

• Reverse causality bias: When it is unclear whether A causes B or B causes A.

• How to calculate and interpret the slope of a line: The slope measures the rate of change between two variables.

Chapter 3. Optimization: Doing the Best You Can

3.1 Two Kinds of Optimization

Optimization can be approached in different ways to achieve the best outcome.

• Optimization in levels: Choosing the best option by comparing total net benefits.

• Optimization in differences: Choosing the best option by comparing marginal (incremental) changes.

3.2 Optimization in Levels

• Comparative statics: Analyzing changes in outcomes resulting from changes in parameters.

• Total cost curves with different opportunity costs of time: Graphical representation of total costs as opportunity costs change.

Chapter 4. Demand, Supply, and Equilibrium

4.1 Markets

Markets are institutions where buyers and sellers interact to exchange goods and services.

• Perfectly competitive markets: Many buyers and sellers, identical products, no single agent can influence the price.

4.2 How Do Buyers Behave? (Demand)

Buyers' decisions are influenced by preferences, prices, and other factors.

• Quantity demanded: The amount of a good buyers are willing and able to purchase at a given price.

• Demand schedule: A table showing quantity demanded at different prices.

• Demand curve: A graph showing the relationship between price and quantity demanded.

• Willingness to pay: The maximum price a buyer will pay for a good.

• Diminishing marginal benefit: Each additional unit consumed provides less additional benefit.

• The Law of Demand: As price falls, quantity demanded rises, ceteris paribus.

• Aggregating individual demand curves: Summing individual demands to get the market demand curve.

• Shifting the demand curve: Factors include:

  • Tastes and preferences

  • Income and wealth

  • Availability and prices of related goods (complements and substitutes)

  • Number and scale of buyers

  • Buyers' beliefs about the future

• Movement along vs. shift of the demand curve: Change in price causes movement along; other factors cause shifts.

4.3 How Do Sellers Behave? (Supply)

Sellers' decisions depend on costs, technology, and market conditions.

• Quantity supplied: The amount of a good sellers are willing to sell at a given price.

• Supply schedule: A table showing quantity supplied at different prices.

• Supply curve: A graph showing the relationship between price and quantity supplied.

• Willingness to accept: The minimum price a seller will accept for a good.

• The Law of Supply: As price rises, quantity supplied rises, ceteris paribus.

• Aggregating individual supply curves: Summing individual supplies to get the market supply curve.

• Shifting the supply curve: Factors include:

  • Prices of inputs

  • Technology

  • Number and scale of sellers

  • Sellers' beliefs about the future

4.4 Supply and Demand in Equilibrium

Market equilibrium occurs where quantity supplied equals quantity demanded.

• Competitive equilibrium price: The price at which the market clears.

• Competitive equilibrium quantity: The quantity bought and sold at equilibrium price.

• Excess supply: Quantity supplied exceeds quantity demanded (surplus).

• Excess demand: Quantity demanded exceeds quantity supplied (shortage).

• Curve shifting in competitive equilibrium: Analyze changes using four steps:

  1. Does the event affect supply or demand?

  2. Is it a shift or a movement along the curve?

  3. Does supply/demand shift to the left or right?

  4. What happens to equilibrium price and quantity?

• Government intervention: Price ceilings and price floors can disrupt equilibrium (e.g., government sets price of gasoline).

Chapter 5. Consumers and Incentives

5.1 The Buyer's Problem

Consumers aim to maximize utility given their budget constraints.

• Total utility and marginal utility: Total utility is the overall satisfaction from consumption; marginal utility is the additional satisfaction from consuming one more unit.

• Law of diminishing marginal utility: Marginal utility decreases as more of a good is consumed.

• The buyer's problem:

  1. What do you like? (Preferences)

  2. How much does it cost? (Prices)

  3. How much money do you have? (Income)

• The budget set and the budget constraint: The set of all affordable consumption bundles given prices and income.

• Draw a budget constraint, calculate slope and opportunity costs: The slope of the budget line is $-\frac{P_x}{P_y}$, representing the opportunity cost of one good in terms of the other.

• Budget constraint pivots if one of the prices changes (slope changes); shifts if income changes (slope does not change).

5.2 Putting It All Together

At the optimal choice, two conditions must hold:

• Marginal benefit per dollar is equalized across goods: $\frac{MB_x}{P_x} = \frac{MB_y}{P_y}$

• The entire income is spent.

5.3 From the Buyer's Problem to the Demand Curve

The individual demand curve is derived from optimal decisions given a budget constraint.

5.4 Consumer Surplus

Consumer surplus measures the benefit consumers receive from purchasing a good at a price lower than their willingness to pay.

• Willingness to pay: The maximum price a consumer is willing to pay for a good or service.

• Consumer surplus (CS) for an individual: The difference between willingness to pay and the market price.

• CS for the market: The area under the demand curve and above the price, calculated as the area of a triangle: $CS = \frac{1}{2} \times \text{base} \times \text{height}$