Economics · Grade 12 · Price Discovery: Supply and Demand · Term 1

Price Elasticity of Supply

Measuring the responsiveness of producers to changes in price.

• Ontario Curriculum Expectations
• CEE.EE.5.3
• CEE.EE.5.4

About This Topic

Price elasticity of supply measures how responsive producers are to price changes. Students calculate it using the formula: percentage change in quantity supplied divided by percentage change in price. Values greater than one indicate elastic supply, between zero and one inelastic supply, and exactly one unit elastic supply. Grade 12 learners apply this to industries like agriculture, which shows low elasticity in the short term due to fixed factors, and manufacturing, which adjusts more readily.

This topic fits the Ontario Economics curriculum's Price Discovery unit, where students explore key questions: calculating PES for industries, analyzing time's impact on elasticity, and identifying determining factors such as spare capacity, input mobility, and production timelines. Short-run supply remains somewhat inelastic, while long-run supply becomes more elastic as firms enter or expand. These concepts prepare students for economic policy analysis, like effects of price floors or taxes on producers.

Active learning suits this topic well. Role-plays and data simulations let students test producer decisions under price shifts, making abstract calculations concrete. Collaborative graphing reinforces factor analysis, while real-world cases build intuition for time-based changes, deepening understanding beyond rote formulas.

Key Questions

1. Calculate the price elasticity of supply for different industries.
2. Analyze how time affects the elasticity of supply for producers.
3. Explain the factors that determine the elasticity of supply.

Learning Objectives

• Calculate the price elasticity of supply for at least two different industries using provided data sets.
• Analyze the impact of varying time horizons (short-run vs. long-run) on the price elasticity of supply for a specific product.
• Explain how factors such as production capacity, input availability, and production flexibility influence a producer's ability to respond to price changes.
• Compare the price elasticity of supply between a primary agricultural product and a manufactured good, justifying the differences observed.
• Evaluate the potential consequences of a sudden price increase on the supply decisions of firms with elastic versus inelastic supply.

Before You Start

Introduction to Supply

Why: Students must understand the basic concept of supply and the law of supply before they can analyze its responsiveness to price changes.

Percentage Change Calculations

Why: The calculation of price elasticity of supply relies directly on the ability to accurately compute percentage changes in both price and quantity.

Factors Affecting Supply

Why: Prior knowledge of what causes shifts in the supply curve is foundational for understanding why supply might be more or less responsive to price changes.

Key Vocabulary

Price Elasticity of Supply (PES)	A measure of how much the quantity supplied of a good or service changes in response to a change in its price. It is calculated as the percentage change in quantity supplied divided by the percentage change in price.
Elastic Supply	Occurs when the percentage change in quantity supplied is greater than the percentage change in price (PES > 1). Producers can easily and quickly increase production.
Inelastic Supply	Occurs when the percentage change in quantity supplied is less than the percentage change in price (PES < 1). Producers find it difficult or slow to increase production.
Unit Elastic Supply	Occurs when the percentage change in quantity supplied is exactly equal to the percentage change in price (PES = 1). The responsiveness is proportional.
Short-run Supply	The period during which at least one factor of production is fixed, limiting a firm's ability to adjust its output significantly in response to price changes.
Long-run Supply	The period during which all factors of production can be varied, allowing firms to adjust their output more fully to price changes, often through entry or exit.

Watch Out for These Misconceptions

Common Misconception

Price elasticity of supply is always elastic across all industries.

What to Teach Instead

Elasticity varies by industry and time frame; short-run agriculture is inelastic due to fixed inputs. Simulations where students role-play producers under time constraints reveal these differences, correcting overgeneralizations through direct comparison.

Common Misconception

Price elasticity of supply measures consumer demand response.

What to Teach Instead

PES focuses on producers' quantity supplied changes; demand elasticity concerns buyers. Paired graphing activities distinguish curves and calculations, helping students separate supply-side responsiveness via visual and computational practice.

Common Misconception

PES values can be negative.

What to Teach Instead

PES is always positive since higher prices prompt more supply. Graphing exercises with real data points clarify the upward slope of supply curves, as students plot and interpret midpoints correctly in groups.

Active Learning Ideas

Simulation Game: Producer Decision Rounds

Divide class into industry groups: agriculture, tech, oil. Announce sequential price changes; groups discuss factors and report new quantity supplied. Calculate class PES for each round and plot on shared graph. Debrief on time effects.

45 min·Small Groups

Graphing Pairs: Elasticity Scenarios

Pairs receive supply schedules for short-run and long-run cases. Plot curves, select points, and compute PES. Switch scenarios midway and compare results. Share one insight per pair with class.

30 min·Pairs

Case Study Stations: Industry Analysis

Set up stations for three industries with data packets on price changes and QS responses. Small groups rotate, calculate PES, note factors, and time influences. Present findings in gallery walk.

50 min·Small Groups

Formal Debate: Elastic vs Inelastic Factors

Assign half class elastic factors, half inelastic. Whole class debates application to a new industry price shock, citing evidence. Vote and calculate hypothetical PES.

35 min·Whole Class

Real-World Connections

• Oil producers in Alberta must consider the long-run price elasticity of supply when deciding on new well investments. If global prices rise, it takes years to develop new extraction sites, making short-run supply less responsive.
• Farmers growing seasonal produce like strawberries face inelastic supply in the immediate weeks after planting, as they cannot quickly increase the harvest. However, over several months, they can adjust planting for future seasons, increasing long-run elasticity.
• Manufacturers of smartphones can often adjust production more readily than farmers. If demand and prices surge, they may have spare factory capacity or can retool assembly lines within weeks, demonstrating a higher price elasticity of supply.

Assessment Ideas

Quick Check

Present students with a scenario: 'The price of lumber increased by 10%, and the quantity supplied increased by 25%.' Ask them to calculate the PES and state whether the supply is elastic, inelastic, or unit elastic. Then, ask them to identify one factor that might explain this elasticity.

Discussion Prompt

Pose this question: 'Imagine a sudden frost damages half the orange crop in Florida. How would the price elasticity of supply for oranges differ in the week after the frost compared to six months later? Explain your reasoning, considering factors like storage and replanting.' Facilitate a class discussion comparing short-term and long-term responses.

Exit Ticket

Provide students with a table listing three industries (e.g., artisanal cheese, electric cars, basic wheat farming). Ask them to assign a PES value (e.g., 0.5, 1.2, 2.5) to each industry and write one sentence justifying their choice based on production characteristics.

Frequently Asked Questions

How do you calculate price elasticity of supply?

Use the midpoint formula: PES = (% change in quantity supplied) / (% change in price), where % change = (new - old) / average of new and old. For example, if price rises from $10 to $12 and QS from 100 to 120 units, PES = [(20/110) / (2/11)] ≈ 1.0, unit elastic. Practice with industry data builds accuracy for policy predictions.

What factors determine the price elasticity of supply?

Key factors include spare production capacity, time to adjust (short vs long run), mobility of inputs, and storage ability. Industries with flexible plants, like apparel, have elastic supply; land-based farming does not. Students analyze these through cases to see how they enable or limit quantity responses to price shifts.

How does time affect the elasticity of supply?

Supply is perfectly inelastic in the immediate market period (fixed QS), somewhat elastic in the short run (some adjustments possible), and highly elastic in the long run (new firms enter). This progression reflects increasing producer flexibility. Timeline activities help students sequence examples like crop harvests versus factory expansions.

How can active learning help students understand price elasticity of supply?

Active methods like producer simulations and graphing stations make PES tangible by letting students enact decisions under price changes and compute real-time elasticities. Group debates on factors and time frames clarify nuances, while case rotations connect theory to industries. These approaches boost retention, as students discover patterns collaboratively rather than memorize formulas, fostering economic intuition for Grade 12 applications.