Economics · Year 12 · The Economic Problem and Markets · Autumn Term

Price Elasticity of Supply (PES) Calculation

Students investigate how responsive producers are to changes in price and calculate Price Elasticity of Supply.

• National Curriculum Attainment Targets
• A-Level: Economics - Price, Income and Cross-Elasticities of Demand
• A-Level: Economics - Supply Analysis

About This Topic

Price Elasticity of Supply (PES) measures the responsiveness of quantity supplied to a change in price. Year 12 students calculate PES with the formula: percentage change in quantity supplied divided by percentage change in price. They classify supply as elastic if PES exceeds 1, inelastic if below 1, or unit elastic if equal to 1. This topic fits within the A-Level Economics focus on supply analysis and elasticities, linking directly to the economic problem and markets unit during Autumn Term.

Students analyze factors that determine PES, such as spare capacity, time period, and factor mobility. They evaluate how elastic supply allows quick market adjustments to price signals, while inelastic supply causes prolonged shortages or surpluses. Firms use PES insights to plan production responses, informing decisions on investment and output. Key questions guide evaluation of market implications and firm strategies.

Active learning benefits this topic because calculations and concepts come alive through data manipulation and simulations. Students grasp abstract responsiveness by plotting supply curves, debating real-world examples like oil or agriculture, and role-playing producer decisions. These methods build analytical confidence and connect theory to policy debates.

Key Questions

1. Analyze the factors that determine the price elasticity of supply for a good.
2. Evaluate the implications of elastic versus inelastic supply for market adjustments.
3. Explain how firms can adjust their production in response to price changes based on PES.

Learning Objectives

• Calculate the Price Elasticity of Supply (PES) for a given product using percentage changes in quantity supplied and price.
• Classify the elasticity of supply as elastic, inelastic, or unit elastic based on calculated PES values.
• Analyze the key factors influencing the price elasticity of supply for specific goods, such as agricultural products or manufactured electronics.
• Evaluate the implications of different PES values for producers responding to market price fluctuations.
• Explain how firms can adjust production levels in response to price changes, considering their PES.

Before You Start

Percentage Change Calculation

Why: Students need to be proficient in calculating percentage changes to accurately determine PES.

Introduction to Supply

Why: Understanding the basic concept of supply, the law of supply, and the factors that shift the supply curve is foundational for analyzing supply responsiveness.

Key Vocabulary

Price Elasticity of Supply (PES)	A measure of how much the quantity supplied of a good or service responds 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	Supply where the PES is greater than 1. This means the percentage change in quantity supplied is greater than the percentage change in price, indicating a high responsiveness of producers.
Inelastic Supply	Supply where the PES is less than 1. This means the percentage change in quantity supplied is less than the percentage change in price, indicating a low responsiveness of producers.
Unit Elastic Supply	Supply where the PES is exactly equal to 1. The percentage change in quantity supplied is equal to the percentage change in price.
Factor Mobility	The ease with which factors of production (like labor, capital, and raw materials) can be moved between different uses or industries. High factor mobility generally leads to more elastic supply.

Watch Out for These Misconceptions

Common Misconception

PES is always greater than PED.

What to Teach Instead

PES and PED measure different sides of the market and vary independently. Active graphing tasks help students plot both curves side-by-side, revealing how supply elasticity depends on production factors, not just demand. Peer discussions clarify this distinction through real data examples.

Common Misconception

Supply is perfectly elastic in the short run.

What to Teach Instead

Short-run supply is often inelastic due to fixed capacity. Simulations where groups adjust output slowly under time constraints demonstrate this, helping students internalize time as a key factor via hands-on trial and error.

Common Misconception

PES formula uses averages only for precision.

What to Teach Instead

While arc elasticity uses averages for large changes, point elasticity applies directly. Calculation stations with varied data sets let students practice both methods, building fluency and spotting when approximations matter in evaluations.

Active Learning Ideas

Data Stations: PES Calculations

Prepare stations with tables showing price and quantity supplied data for goods like coffee and smartphones. Pairs calculate PES at each station, plot points on graphs, and classify elasticity. They rotate stations and compare results in a class share-out.

45 min·Pairs

Market Simulation: Producer Responses

Divide small groups into firms producing elastic or inelastic goods. Announce price changes; groups decide output adjustments based on PES factors and recalculate PES. Debrief on market equilibrium shifts.

50 min·Small Groups

Graphing Challenge: Elasticity Curves

Individuals receive supply schedules for different time periods. They graph curves, calculate PES at points, and label elastic/inelastic sections. Pairs then peer-review and discuss factor influences.

30 min·Individual

Debate Carousel: Elastic vs Inelastic

Whole class rotates through stations debating implications of PES for policy (e.g., taxes on elastic goods). Each group prepares arguments using calculations, then votes on strongest cases.

40 min·Whole Class

Real-World Connections

• Oil producers, like those in Saudi Arabia or Russia, face decisions about increasing output when global prices rise. Their ability to quickly ramp up production depends on spare capacity and the mobility of extraction resources, influencing their PES.
• Farmers supplying fresh produce to markets like Borough Market in London must respond to daily price changes. The PES for perishable goods like strawberries is often inelastic in the short term due to growing cycles and limited storage, impacting how quickly supply can meet demand shifts.
• Manufacturers of complex electronics, such as smartphone companies in South Korea or Taiwan, must consider their PES when faced with sudden demand surges. The availability of specialized components and skilled labor affects how quickly they can adjust production volumes.

Assessment Ideas

Quick Check

Present students with two scenarios: Scenario A shows a 10% price increase leading to a 20% increase in quantity supplied. Scenario B shows a 10% price increase leading to a 5% increase in quantity supplied. Ask students to calculate the PES for each scenario and classify the supply as elastic or inelastic.

Exit Ticket

Provide students with a hypothetical good, for example, 'artisanal bread'. Ask them to: 1. State whether they believe the PES for artisanal bread is likely to be elastic or inelastic, and briefly explain why. 2. Suggest one factor that would make its supply more elastic and one factor that would make it more inelastic.

Discussion Prompt

Facilitate a class discussion using the prompt: 'Imagine the price of concert tickets for a popular band doubles. How might the Price Elasticity of Supply for these tickets differ from the PES for basic household furniture? What factors explain these differences?' Encourage students to use key vocabulary in their responses.

Frequently Asked Questions

How do you calculate Price Elasticity of Supply?

Use PES = (% change in quantity supplied) / (% change in price). For example, if price rises 10% and quantity supplied increases 20%, PES is 2 (elastic). Students practice with tables: compute changes, divide, and interpret. Graphs reinforce by showing slope steepness, linking math to economic intuition in under 10 minutes per set.

What factors determine PES for a good?

Key factors include spare capacity (more capacity means elastic supply), time period (longer allows elastic adjustments), factor mobility, and storage ability. Agriculture often shows inelastic short-run PES due to land limits, while manufactured goods elasticise over time. Classify goods collaboratively to evaluate impacts on firm strategies.

What are the implications of elastic versus inelastic supply?

Elastic supply (PES >1) enables quick equilibrium after shocks, minimizing shortages. Inelastic (PES <1) leads to price spikes or surpluses. Evaluate for policy: taxes on inelastic goods raise more revenue. Role-plays simulate these, showing firm profits and consumer effects clearly.

How can active learning help teach PES calculations?

Active methods like station rotations with real data make PES tangible: students compute, graph, and debate elasticity live. Simulations of price shocks reveal factor influences dynamically. This beats lectures by fostering ownership; misconceptions fade as peers challenge ideas, boosting retention for A-Level evaluations (60-70% improvement in understanding per studies).