IB Economics 2.7.2: Price Controls - Ceilings, Floors, Diagrams & HL Calculations

Main Ideas

1. What Price Controls Are

Price controls are government-set minimum or maximum prices that prevent a market price from reaching its free-market equilibrium. This creates disequilibrium in the form of a shortage or surplus.

• A price ceiling is a legal maximum price. It is generally set below equilibrium to prevent a good or service from becoming unaffordable.
• A price floor is a legal minimum price. It is generally set above equilibrium to prevent prices from becoming too low.

The presenter’s memory aid is that the terms are “flipped”: a ceiling is below equilibrium, while a floor is above it.

2. Price Ceilings

Rent control is a common example of a price ceiling.

Market effects

At the controlled price, consumers demand more while firms supply less. Quantity demanded therefore exceeds quantity supplied, creating a shortage.

Because price no longer rations goods to those willing to pay the most, alternative allocation methods may emerge, such as queues, lotteries, or favoritism. Shortages may also encourage illegal resale or black markets, where goods are sold above the legal ceiling—and potentially above the free-market price.

A ceiling reduces the quantity supplied below the socially efficient level. The presenter describes this as underallocation of resources and a loss of social welfare. In the diagram, consumer surplus is shown as areas A and C, producer surplus as E, and welfare loss as areas B and D.

Effects on stakeholders

• Consumers: Those who obtain the good pay less and may benefit, but others cannot obtain it and remain unsatisfied. Consumer outcomes are mixed.
• Producers: Usually worse off because they sell fewer units at a lower price, reducing revenue and producer surplus.
• Workers: Lower production can reduce firms’ demand for labor, increasing unemployment or reducing hiring.
• Government: May gain political support from consumers, while illegal transactions can lead to lost tax revenue.

Rent control in particular: Lower rents may make housing more affordable for some low-income tenants, but can also lead to waiting lists, overcrowding, reduced landlord maintenance, and subletting at higher illegal rents. Removing rent controls could leave some low-income households unable to afford housing, potentially contributing to wider social problems.

3. Price Floors for Agricultural Products

Governments may set agricultural price floors to support farmers and encourage food production.

Market effects

When a price floor is set above equilibrium, producers are willing to supply more while consumers demand less, creating a surplus. The government may buy the excess output, guaranteeing farmers a market and potentially encouraging production to support food security.

Government purchases have an opportunity cost: tax money used to buy surplus goods cannot be spent elsewhere. Storing the surplus costs money and risks spoilage. Exporting it can be difficult because the supported price may be too high to compete internationally; governments may also use subsidies, adding further expense.

The presenter argues that guaranteed sales can weaken firms’ incentives to cut costs, innovate, or use resources efficiently. Producing more than society wants also creates allocative inefficiency. In the diagram, consumers lose surplus while producers gain. Although the diagram shows a producer gain, government spending on unwanted output creates a wider social cost.

Effects on stakeholders

• Consumers: Pay a higher price and buy a smaller quantity.
• Farmers and producers: Receive a higher price and can sell the surplus to the government, raising revenue and providing protection from competition and volatile prices.
• Workers: Higher production may increase demand for agricultural labor.
• Government and taxpayers: Fund purchases, storage, and possibly subsidies, leaving less money for other purposes.
• Other countries: If many governments export surpluses, global supply may rise and world prices may fall. The presenter says this can be especially damaging to less-developed countries that rely heavily on agricultural exports.

4. Minimum Wages as a Price Floor in the Labor Market

A minimum wage is a price floor in the labor market, intended to protect low-income workers.

If set above the equilibrium wage, more people are willing to work while firms demand fewer workers. This creates excess supply of labor, or unemployment. The presenter breaks this surplus into:

• A fall in labor demanded by firms, from the equilibrium quantity to the lower quantity demanded at the minimum wage.
• An increase in labor supplied, from the equilibrium quantity to the higher quantity supplied at the minimum wage.

Higher wages raise firms’ production costs, potentially reducing hiring and output. These effects are most relevant to low-wage, low-skilled jobs. Some firms might illegally hire workers below the minimum wage, creating a black market for labor.

Effects on stakeholders

• Firms: Face higher costs.
• Workers: Those who keep or gain jobs earn more, while others may become unemployed.
• Consumers: May face higher prices or reduced output.

The presenter notes that economists generally recognize minimum wages as a way to improve equity and income distribution. Debate focuses partly on how high they should be: studies are said to suggest that a minimum wage not set too far above equilibrium may have little effect—or even a positive effect—on unemployment.

5. Overall Evaluation

Price controls can provide short-term protection for groups such as tenants, workers, or farmers. However, they can also cause shortages, surpluses, inefficiency, and unintended effects on other stakeholders. The presenter emphasizes that exam answers should evaluate both benefits and costs, including longer-term consequences, rather than treating controls as wholly good or bad.

HL Calculation Methods and Worked Examples

General Calculation Approach

• Shortage: Quantity demanded − quantity supplied
• Surplus: Quantity supplied − quantity demanded
• Expenditure or revenue: Price × quantity

For a ceiling, the quantity actually traded is limited by supply. Consumer expenditure and producer revenue therefore use the supplied quantity.

For a floor where the government buys the surplus:

• Consumer expenditure uses the quantity consumers buy.
• Producer revenue includes both consumer purchases and government purchases.
• Government expenditure is the floor price multiplied by the surplus it buys.

For surplus areas, use triangle or trapezoid formulas as appropriate, then compare values before and after the control to find changes. The presenter calculates welfare loss using the labeled areas in the diagrams.

Price-Ceiling Example

Given an equilibrium price of $4, an equilibrium quantity of 20,000 units per week, and a ceiling of $2.50:

• Quantity demanded rises to 30,000; quantity supplied falls to 10,000.
• Shortage: 30,000 − 10,000 = 20,000 units per week.
• Consumer expenditure at equilibrium: $4 × 20,000 = $80,000.
• Expenditure after the ceiling: $2.50 × 10,000 = $25,000, a reported decrease of $55,000.
• Producer revenue falls by the same amount, from $80,000 to $25,000.
• Consumer surplus rises from $30,000 to $37,500, a reported gain of $7,500.
• Producer surplus falls from $40,000 to $12,500, a reported loss of $27,500.
• The presenter calculates welfare loss as $15,000.

Price-Floor Example

Given an equilibrium price of $10, an equilibrium quantity of 300 units, a floor of $13, quantity demanded of 200, and quantity supplied of 400:

• Surplus: 400 − 200 = 200 units.
• Consumer expenditure falls from $10 × 300 = $3,000 to $13 × 200 = $2,600, a decrease of $400.
• Producer revenue before the floor is $3,000. With the government buying the surplus, revenue becomes $13 × 400 = $5,200, an increase of $2,200.
• Government expenditure: $13 × 200 surplus units = $2,600.
• Consumer surplus falls from $1,500 to $700, a reported loss of $800.
• Producer surplus rises from $1,500 to $2,600, a reported gain of $1,100.
• Using the diagram’s labeled areas, the presenter reports welfare loss of $2,300.

Speakers and Sources Featured

The lesson is presented by one instructor/narrator in a video from Kevin Means Business. Economists and research studies are mentioned generally in the minimum-wage discussion, but no individual economists or specific studies are named. No guest speakers are featured.