Microeconomics Study Guide: Demand, Supply, Market Equilibrium, and Market Interventions

Chapter 3: Demand, Supply, and Market Equilibrium

Supply Shifters

The supply curve shows the relationship between the price of a good and the quantity supplied. Several factors can shift the supply curve, changing the market outcome.

• Prices of Inputs: An increase in input prices (e.g., labor, raw materials) raises production costs, shifting supply left (decrease). A decrease shifts supply right (increase).

• Technological Change: Improvements in technology make production more efficient, shifting supply right.

• Prices of Related Goods in Production: If a firm can produce multiple goods, a rise in the price of one may shift supply of the other.

• Number of Firms in the Market: More firms increase supply (right shift); fewer firms decrease supply (left shift).

• Expected Future Prices: If producers expect higher prices in the future, they may decrease current supply (left shift).

• Natural Disasters and Pandemics: Events that disrupt production shift supply left.

Example: A new technology reduces production costs for smartphones, shifting the supply curve right and lowering equilibrium price while increasing equilibrium quantity.

Substitutes and Complements

Understanding how related goods affect demand is crucial for predicting market changes.

• Substitutes: Goods that can replace each other. A rise in the price of one increases demand for the other (e.g., butter and margarine).

• Complements: Goods consumed together. A rise in the price of one decreases demand for the other (e.g., printers and ink cartridges).

Example: If the price of coffee rises, demand for tea (a substitute) increases.

Normal and Inferior Goods

Income changes affect demand differently depending on the type of good.

• Normal Goods: Demand increases as income rises (e.g., organic food).

• Inferior Goods: Demand decreases as income rises (e.g., instant noodles).

Example: During an economic boom, demand for restaurant meals (normal good) rises, while demand for bus rides (inferior good) falls.

Double Shifters

When both supply and demand shift simultaneously, the effect on equilibrium price and quantity can be clear or ambiguous.

• If both supply and demand increase (shift right), equilibrium quantity will definitely rise, but the effect on price is ambiguous.

• If supply increases and demand decreases, price will fall, but the effect on quantity is ambiguous.

Example: New technology (supply right) and increased consumer preference (demand right) for electric cars: quantity rises, price change is uncertain.

Law of Demand

The law of demand states that, all else equal, as the price of a good falls, the quantity demanded rises.

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

• Change in Demand: Shift of the entire demand curve due to factors like income, tastes, or prices of related goods.

Example: A decrease in the price of apples leads to a higher quantity demanded (movement along the curve).

Market Equilibrium and Adjustments

Market equilibrium occurs where quantity demanded equals quantity supplied. Disequilibrium leads to price adjustments.

• Surplus (Excess Supply): When supply exceeds demand, price falls.

• Shortage (Excess Demand): When demand exceeds supply, price rises.

Example: If a surplus of wheat occurs, farmers lower prices to sell excess stock.

Demand and Supply as Marginal Curves

The demand curve represents marginal benefit (MB), and the supply curve represents marginal cost (MC). Efficiency occurs at their intersection.

• Marginal Benefit: The additional benefit from consuming one more unit.

• Marginal Cost: The additional cost of producing one more unit.

• Efficiency: Occurs where $MB = MC$.

Example: At equilibrium, the last unit traded provides equal benefit and cost.

Demand Shifters

Several factors can shift the demand curve.

• Tastes and Preferences: Changes in consumer preferences shift demand.

• Income Changes: Affect demand for normal and inferior goods.

• Prices of Related Goods: Substitutes and complements affect demand.

• Expectations about the Future: Anticipated price changes shift demand.

• Market Size: More buyers increase demand.

Example: A health trend increases demand for kale.

Chapter 4: Market Interventions and Efficiency

Price Ceilings and Price Floors

Governments may set legal maximum (ceiling) or minimum (floor) prices to influence market outcomes.

• Price Ceiling: Maximum legal price (e.g., rent control).

• Price Floor: Minimum legal price (e.g., minimum wage).

• Binding: A ceiling is binding if set below equilibrium price; a floor is binding if set above equilibrium price.

• Effects: Binding ceilings cause shortages; binding floors cause surpluses.

Example: A binding rent ceiling leads to apartment shortages.

Effects on Consumer and Producer Surplus

Market interventions change the distribution of benefits between consumers and producers.

• Consumer Surplus (CS): The difference between willingness to pay and actual price.

• Producer Surplus (PS): The difference between actual price and minimum acceptable price.

• Deadweight Loss (DWL): Loss of total surplus due to inefficiency.

Example: A price floor reduces consumer surplus and creates deadweight loss.

Taxes

Taxes affect market outcomes and efficiency. The burden (tax incidence) depends on elasticity, not who pays the tax.

• Tax Incidence: The division of tax burden between buyers and sellers.

• Graphing a Per-Unit Tax: The supply curve shifts up by the amount of the tax.

• Calculating Tax Revenue: $\text{Tax Revenue} = \text{Tax per unit} \times \text{Quantity sold}$

• Deadweight Loss: The reduction in total surplus due to the tax.

Example: A $2 per-unit tax on cigarettes reduces quantity sold and creates deadweight loss.

Consumer Surplus

Consumer surplus measures the net benefit to consumers from market transactions.

• Formula: $\text{CS} = \text{Willingness to Pay} - \text{Actual Price}$

• Can be calculated for individuals or groups.

Example: If a consumer is willing to pay $10 for a product sold at $7, CS = $3.

Economic Efficiency

Efficiency is achieved when resources are allocated so that marginal benefit equals marginal cost.

• Efficiency Point: $MB = MC$ at the last unit traded.

• Interventions (ceilings, floors, taxes) move the market away from efficiency, creating deadweight loss.

Example: A tax reduces the number of units traded, causing deadweight loss.

Summary Table: Effects of Market Interventions

Intervention	Binding Condition	Effect on Price	Effect on Quantity	Consumer Surplus	Producer Surplus	Deadweight Loss
Price Ceiling	Set below equilibrium	Lower	Lower	May increase for some, decrease overall	Decrease	Yes
Price Floor	Set above equilibrium	Higher	Lower	Decrease	May increase for some, decrease overall	Yes
Tax	Applied to buyers or sellers	Buyers pay more, sellers receive less	Lower	Decrease	Decrease	Yes

Additional info: Table entries inferred for clarity and completeness.