Quick Summary
- Elastic supply means suppliers respond strongly to price changes
- Inelastic supply means quantity supplied barely changes despite price changes
- Time period is crucial – supply becomes more elastic over longer periods
- Availability of raw materials affects how easily supply can increase
- Agricultural products tend to have inelastic supply in the short run
What Is Elasticity of Supply?
Elasticity of supply shows how responsive producers are when prices change. If tomato prices rise from ₦200 to ₦400 per kilo, will farmers supply much more? The answer depends on supply elasticity.
Some goods have very responsive supply. When prices rise, suppliers quickly produce more. Other goods have stubborn supply. Even when prices double, suppliers can’t produce much more.
Understanding this concept helps explain why some shortages last longer than others in Nigeria. When petrol prices rise, supply doesn’t immediately increase because building new refineries takes years. But when prices of imported electronics rise, suppliers can quickly bring in more stock.
How to Calculate Elasticity of Supply
The formula is:
Elasticity of Supply (Es) = Percentage Change in Quantity Supplied ÷ Percentage Change in Price
Or written mathematically:
Es = (ΔQ/Q × 100) ÷ (ΔP/P × 100)
Where:
ΔQ = Change in quantity supplied
Q = Original quantity supplied
ΔP = Change in price
P = Original price
Worked Example
A shoe manufacturer in Aba produces 1,000 pairs of shoes monthly when the price is ₦5,000 per pair. When price rises to ₦6,000, he increases production to 1,300 pairs. What is the elasticity of supply?
Step 1: Calculate percentage change in quantity
Change in quantity = 1,300 – 1,000 = 300
Percentage change = (300/1,000) × 100 = 30%
Step 2: Calculate percentage change in price
Change in price = ₦6,000 – ₦5,000 = ₦1,000
Percentage change = (1,000/5,000) × 100 = 20%
Step 3: Calculate elasticity
Es = 30% ÷ 20% = 1.5
This means supply is elastic. When price rises by 1%, quantity supplied rises by 1.5%.
Types of Supply Elasticity
1. Perfectly Elastic Supply (Es = ∞)
Suppliers will provide any quantity at a particular price, but nothing at a lower price. The supply curve is horizontal. This is rare in real life but occurs in perfectly competitive markets where many sellers offer identical products.
Example: If you’re selling identical sachets of pure water at a bus stop with 20 other sellers, you must match their price exactly. If you charge even ₦5 more, you sell nothing.
2. Elastic Supply (Es > 1)
Quantity supplied changes by a larger percentage than price. Suppliers are very responsive.
Example: Electronics in Computer Village, Lagos. When phone prices rise 10%, traders can quickly import 20% more stock because they have established supply chains and warehouses.
3. Unitary Elastic Supply (Es = 1)
Percentage change in quantity supplied equals percentage change in price. A 15% price rise causes a 15% supply increase.
Example: Some manufactured goods with standard production times and steady raw material availability.
4. Inelastic Supply (Es < 1)
Quantity supplied changes by a smaller percentage than price. Suppliers struggle to respond quickly.
Example: Fresh fish in Nigerian markets. Even if prices triple, fishermen can’t immediately catch much more fish. They’re limited by boat capacity, fishing grounds, and weather.
5. Perfectly Inelastic Supply (Es = 0)
Quantity supplied stays the same regardless of price changes. The supply curve is vertical.
Example: Original paintings by a deceased artist like Aina Onabolu. No matter how high prices go, no new paintings can be created. Land in a specific location (like Lekki Phase 1) is also perfectly inelastic – there’s only so much land there.
Factors Affecting Elasticity of Supply
1. Time Period
This is the most important factor. Supply becomes more elastic over time.
Immediate period (market period): Supply is fixed. A yam farmer who brought 100 tubers to market cannot get more today, even if prices double. Supply is perfectly inelastic.
Short run: Some adjustments possible. The farmer can harvest more from existing farms next week. Supply becomes slightly elastic.
Long run: Full adjustments possible. Farmers can clear more land, plant more crops, buy tractors. Supply becomes very elastic.
This explains why food shortages often follow bad harvests in Nigeria. Farmers can’t quickly replace destroyed crops, so supply remains low despite high prices until the next planting season.
2. Availability of Raw Materials
If raw materials are easy to get, supply is elastic. Producers can quickly make more.
Example: Sachet water producers in Nigeria can easily increase supply because water and nylon sachets are readily available. But steel manufacturers struggle to increase supply quickly because they must import iron ore, which takes time.
3. Spare Production Capacity
Firms with unused capacity can quickly increase supply. Their supply is elastic.
Example: During COVID-19, some Nigerian garment factories had idle machines. When demand for face masks exploded, they quickly switched production. Factories running at full capacity couldn’t respond as fast.
4. Storage Possibilities
Goods that can be stored have more elastic supply. When prices rise, sellers release stored stocks.
Example: Rice can be stored for months. When prices rise, traders supply more from warehouses. Fresh tomatoes rot quickly, so supply can’t adjust easily through storage.
5. Ease of Factor Mobility
If workers and machines can easily switch between products, supply is more elastic.
Example: A bakery can quickly switch from making bread to meat pies if prices change. But an oil refinery can’t easily switch to making something else. Its supply is inelastic.
6. Nature of Production
Agricultural products typically have inelastic supply because production depends on seasons. You can’t rush crop growth.
Manufactured goods often have elastic supply because factories can add shifts, hire more workers, or install more machines.
7. Government Regulations
Licenses, quotas, and regulations make supply inelastic. Suppliers can’t respond to price signals if regulations block them.
Example: If government limits the number of taxi licenses in Lagos, supply remains fixed even when prices rise. But in areas without such limits, supply increases when fares rise.
Comparison Table: Elastic vs. Inelastic Supply
| Feature | Elastic Supply | Inelastic Supply |
|---|---|---|
| Elasticity Value | Greater than 1 (Es > 1) | Less than 1 (Es < 1) |
| Response to Price | Quantity changes MORE than price | Quantity changes LESS than price |
| Time Required | Long run – plenty of time | Short run – little time |
| Raw Materials | Easily available | Scarce or hard to get |
| Production | Can be increased quickly | Slow to increase |
| Examples | Electronics, imported goods, manufactured items | Fresh vegetables, original artwork, skilled labor |
| Supply Curve | Flatter (more horizontal) | Steeper (more vertical) |
Importance of Supply Elasticity
For Government: Knowing supply elasticity helps plan policies. Taxing goods with inelastic supply generates more revenue because quantity doesn’t fall much. Nigeria’s government knows petrol supply is inelastic in the short run, which is partly why fuel is heavily taxed.
For Producers: Understanding their own supply elasticity helps businesses plan. If you can quickly increase supply when prices rise, you can capture more profit.
For Consumers: Inelastic supply means shortages last longer and prices stay high. When floods destroy yam farms in Benue, consumers face high prices for months because supply can’t adjust quickly.
Common Exam Mistakes
WAEC Examiners Report:
- Confusing elasticity of supply with elasticity of demand: Many students mix up these concepts. Supply elasticity is about producers, demand elasticity is about consumers.
- Wrong formula application: Students often divide price change by quantity change instead of the reverse. Remember: percentage change in QUANTITY ÷ percentage change in PRICE.
- Forgetting to convert to percentages: You must calculate percentage changes, not just absolute changes.
- Missing the time factor: When explaining factors affecting supply elasticity, many students forget that time is the most critical factor.
- Using wrong elasticity terms: Saying “supply is high” instead of “supply is elastic.” Use correct economic terminology.
- Poor diagram labeling: When drawing supply curves, students forget to label axes as “Price” and “Quantity” or fail to show which curve is more elastic.
Practice Questions
Multiple Choice Questions
1. If elasticity of supply is 0.5, then supply is:
a) Perfectly elastic
b) Elastic
c) Inelastic ✓
d) Perfectly inelastic
2. The price of garri rises by 20% and quantity supplied increases by 40%. The elasticity of supply is:
a) 0.5
b) 2.0 ✓
c) 20
d) 40
3. Which factor makes agricultural supply typically inelastic in the short run?
a) High demand
b) Dependence on growing seasons ✓
c) Low prices
d) Government subsidies
4. A vertical supply curve indicates:
a) Elastic supply
b) Unitary elastic supply
c) Perfectly inelastic supply ✓
d) Perfectly elastic supply
5. Over time, supply tends to become:
a) More inelastic
b) More elastic ✓
c) Perfectly inelastic
d) Unchanged
Essay Questions
1. (a) Define elasticity of supply. (2 marks)
(b) Calculate the elasticity of supply if quantity supplied rises from 200 units to 300 units when price increases from ₦1,000 to ₦1,200. (4 marks)
(c) State whether the supply is elastic or inelastic. (1 mark)
Examiner’s tip: Show all calculation steps clearly. Write the formula first, then substitute values, then solve. Don’t skip steps.
2. Explain FIVE factors that determine the elasticity of supply of a commodity. (10 marks)
Examiner’s tip: Must explain, not just list. For each factor, state it clearly (e.g., “Time period”), then explain HOW it affects elasticity (e.g., “In the short run, supply is inelastic because…”). Include an example for each factor. Budget 2 marks per factor.
3. With the aid of diagrams, distinguish between elastic and inelastic supply. (8 marks)
Examiner’s tip: Draw two separate diagrams – one showing elastic supply (flatter curve) and one showing inelastic supply (steeper curve). Label all axes. Define both terms (2 marks total), draw and label diagrams (4 marks), and explain the difference (2 marks).
4. Why is the supply of agricultural products generally inelastic in the short run? Give THREE reasons. (6 marks)
Examiner’s tip: Focus specifically on agriculture. Mention growing seasons, weather dependence, and inability to store fresh produce. Give Nigerian examples like yam or tomato farming.
Memory Aids
Remember the formula with “QP”:
Elasticity = Quantity change ÷ Price change (both in percentages)
For factors affecting elasticity, remember “TRAIN”:
- T – Time period (most important)
- R – Raw materials availability
- A – Availability of spare capacity
- I – Inventory/storage possibilities
- N – Nature of production process
Quick check: If Es > 1, it’s elastic. If Es < 1, it's inelastic. If Es = 1, it's unitary.
Visual memory: Think of “elastic” like a rubber band that stretches a lot. Elastic supply responds a lot to price changes. “Inelastic” is like a stick – it barely bends even when you push hard.
Related Topics
- Elasticity of Demand
- Price Determination in Markets
- Market Equilibrium
- Factors Affecting Supply
- Government Price Controls