Weekly Assignment 4 Microeconomics Study Guide: Price Controls, Market Equilibrium, and Economic Surplus

Market Equilibrium and Quantity Exchanged

Understanding Market Equilibrium

Market equilibrium occurs where the quantity demanded equals the quantity supplied at a particular price. At this point, the market clears, and there is no tendency for the price to change.

• Equilibrium Price: The price at which quantity demanded equals quantity supplied.

• Equilibrium Quantity: The quantity bought and sold at the equilibrium price.

• Quantity Actually Exchanged: At any disequilibrium price, the quantity actually exchanged is determined by the lesser of quantity demanded and quantity supplied.

Example: If at a price of $2, quantity demanded is 100 units and quantity supplied is 150 units, only 100 units will be exchanged.

Price Controls: Price Ceilings and Price Floors

Definitions and Effects

• Price Ceiling: A legal maximum price set below equilibrium, leading to shortages.

• Price Floor: A legal minimum price set above equilibrium, leading to surpluses.

• Binding Price Control: A price control that affects the market outcome (i.e., set below equilibrium for ceilings, above for floors).

Effects of Price Ceilings:

• Creates a shortage (excess demand).

• May lead to rationing, black markets, or non-price allocation mechanisms.

Effects of Price Floors:

• Creates a surplus (excess supply).

• May lead to government purchases of surplus or disposal.

Table: Effects of Price Controls on Market Outcomes

Type of Control	Set Above/Below Equilibrium?	Result
Price Ceiling	Below	Shortage (excess demand)
Price Floor	Above	Surplus (excess supply)

Excess Supply and Excess Demand

Definitions

• Excess Supply (Surplus): Occurs when quantity supplied exceeds quantity demanded at a given price.

• Excess Demand (Shortage): Occurs when quantity demanded exceeds quantity supplied at a given price.

Example: If at $1.80, 2000 units are supplied but only 1600 are demanded, there is a surplus of 400 units.

Application: Chocolate Bar Market Example

Market Data Table

Price ($)	Quantity Demanded (thousands/week)	Quantity Supplied (thousands/week)
2.00	1500	2100
1.80	1600	2050
1.60	1700	2000
1.40	1800	1950
1.20	1900	1900
1.00	2000	1850
0.80	2100	1800
0.60	2200	1750

Equilibrium: At $1.20, quantity demanded equals quantity supplied (1900 thousand bars/week).

Price Ceiling Example: If a price ceiling of $1.00 is imposed, only 1850 thousand bars can be supplied, but 2000 thousand are demanded, resulting in a shortage of 150 thousand bars.

Price Floor Example: If a price floor of $1.80 is imposed, only 1600 thousand bars are demanded, but 2050 thousand are supplied, resulting in a surplus of 450 thousand bars.

Economic Surplus and Deadweight Loss

Definitions

• Consumer Surplus: The difference between what consumers are willing to pay and what they actually pay.

• Producer Surplus: The difference between what producers are paid and their minimum acceptable price.

• Economic Surplus: The sum of consumer and producer surplus; maximized at equilibrium.

• Deadweight Loss: The reduction in economic surplus resulting from market inefficiency, such as price controls.

Graphical Representation: Deadweight loss appears as the area between supply and demand curves that is not realized due to under- or over-production.

Elasticity and Market Adjustment

Price Elasticity of Supply and Demand

• Price Elasticity of Demand: Measures the responsiveness of quantity demanded to a change in price.

• Price Elasticity of Supply: Measures the responsiveness of quantity supplied to a change in price.

• Long-Run vs. Short-Run Elasticity: Supply and demand are generally more elastic in the long run than in the short run.

Formula for Price Elasticity of Demand:

$\text{Price Elasticity of Demand} = \frac{\%\ \text{Change in Quantity Demanded}}{\%\ \text{Change in Price}}$

Formula for Price Elasticity of Supply:

$\text{Price Elasticity of Supply} = \frac{\%\ \text{Change in Quantity Supplied}}{\%\ \text{Change in Price}}$

Government Intervention: Quotas and Subsidies

Production Quotas

• Quota: A government-imposed limit on the quantity of a good that can be produced or sold.

• Quotas can raise prices and reduce total economic surplus.

Subsidies and Guaranteed Prices

• Subsidy: A payment by the government to producers to encourage production.

• Guaranteed Price: The government promises to buy any surplus at a set price, supporting producer incomes but potentially leading to overproduction.

Worked Example: Milk Market

Given:

• Demand: $p = 225 - 15Q^D$

• Supply: $p = 25 + 35Q^S$

Finding Equilibrium:

• Set $Q^D = Q^S = Q$ and solve for $p$ and $Q$:

$225 - 15Q = 25 + 35Q$

$200 = 50Q$

$Q = 4$ (million litres), $p = 225 - 15 \times 4 = 165$ (cents per litre)

Government Guaranteed Price:

• If the government guarantees $p = 200$ (cents per litre):

• Find $Q^D$ and $Q^S$ at $p = 200$:

$Q^D = \frac{225 - 200}{15} = 1.67$ (million litres)

$Q^S = \frac{200 - 25}{35} = 5$ (million litres)

• The government must buy the surplus: $5 - 1.67 = 3.33$ million litres.

Who benefits? Producers benefit from higher prices and guaranteed sales; consumers pay higher prices; taxpayers fund the surplus purchases.

Graphical Analysis: Price Controls and Surplus Redistribution

Interpreting Supply and Demand Diagrams

• Areas under the demand curve and above the price represent consumer surplus.

• Areas above the supply curve and below the price represent producer surplus.

• Imposing price controls redistributes surplus and creates deadweight loss.

Example: A price floor redistributes surplus from consumers to producers and creates deadweight loss (lost surplus).

Short Answer and Application Questions

• Calculate equilibrium price and quantity from given demand and supply equations.

• Analyze the effects of price ceilings and floors using tables and diagrams.

• Determine changes in consumer and producer surplus, and identify deadweight loss areas.

• Discuss who benefits and who is harmed by government interventions.

Additional info: These concepts are foundational for understanding how government policies affect market outcomes, efficiency, and welfare in microeconomics.