Chapter 2 Notes: Perfect Competition and Demand

Perfect competition serves as the baseline model where supply and demand determine prices and quantities. Key market assumptions include identical goods, many price-taking buyers and sellers, no external effects, and perfect information, simplifying the analysis to a single market price.

Demand: The Buyer

as Side
Demand reflects the inverse relationship between price and quantity demanded; as price rises, quantity demanded falls, formalized as $\frac{dQ_d}{dP} < 0$. This Law of Demand is an empirical regularity, tied to consumers' willingness to pay (WTP) and marginal benefit (MB).

Willingness to Pay (WTP) and Marginal Benefit (MB)

WTP for a unit is the maximum price a consumer will pay, equivalent to the marginal benefit (MB) gained from consuming that unit. MB typically decreases with each additional unit (diminishing marginal benefit), meaning $MB<em>1 > MB</em>2 > MB_3 > \dots$. The demand curve graphically represents this WTP across successive units.

The Demand Curve and Ceteris Paribus

The demand curve is the set of all (price, quantity demanded) pairs, where the height at each quantity reflects the MB or WTP for that unit. The principle of ceteris paribus ("all else equal") states that when moving along the demand curve, only price changes, while factors like income, tastes, and prices of related goods remain constant. Changes in these other factors cause the entire demand curve to shift.

Key Concepts

• Demand curve: $Q_d = D(P)$, quantity demanded at each price.

• Law of demand: $\frac{dQ_d}{dP} < 0$.

• Willingness to pay (WTP): Maximum price for a unit; marginal benefit.

• Marginal benefit (MB): Additional satisfaction from an additional unit, typically diminishing ($MB<em>1 > MB</em>2 > \dots$).

• Diminishing marginal utility: Decreasing extra satisfaction from each additional unit consumed.

• Ceteris paribus: All else held constant during analysis. price changes cause movement along the curve; income/tastes cause shifts.