Crux First
What you must remember for MCQs
- Supply = willingness + ability + time element.
- Supply is a flow concept.
- Supply ≠ stock.
- Law of Supply = direct relationship between price and quantity supplied.
- Determinants of supply = price, cost, technology, related goods, government policy, number of sellers, expectations, natural factors.
- Movement in supply = due to price.
- Shift in supply = due to other factors.
- Elasticity of supply = responsiveness of supply to change in price.
- Market supply = horizontal addition of all firms.
- Equilibrium = demand = supply.
1. Meaning of Supply
Definition
- Supply means the quantity a producer is willing and able to offer at different prices during a given time period.
Three Key Points
- Supply is what is offered, not what is sold.
- It requires:
- Supply is a flow concept, so time period is essential.
Example: 100 units per day is supply. Merely having stock is not supply.
MCQ Traps
- Stock is not the same as supply.
- Supply must include a time period.
2. Determinants of Supply
1. Price of the Commodity
- Price rises → supply rises.
- This is the core determinant.
2. Cost of Production
- Cost rises → supply falls.
- Cost falls → supply rises.
- Includes wages, raw material and similar input costs.
3. Technology
- Better technology lowers cost and raises supply.
4. Price of Related Goods
- Competitive goods: If price of substitute good rises, supply of this good may fall.
- Joint goods: Supply moves together.
5. Government Policy
- Tax rises → supply falls.
- Subsidy rises → supply rises.
6. Number of Sellers
- More firms in the market → supply rises.
7. Future Expectations
- If producers expect price to rise in future, they may hold stock now, so present supply falls.
8. Natural Factors
- Especially important in agriculture.
- Weather affects supply.
Important: ICAI often asks determinants of supply directly as a list-based MCQ.
3. Law of Supply
Statement
- Other things remaining constant, price rises and supply rises.
Supply Schedule and Supply Curve
- Supply schedule shows the relationship between price and quantity supplied.
- Supply curve is generally upward sloping.
Why Upward Sloping?
- Profit motive
- Entry of new firms
- Better use of resources
4. Movement vs Shift in Supply
Movement in Supply
- Also called change in quantity supplied.
- Caused by price change only.
- Shown by movement along the same supply curve.
Shift in Supply
- Also called change in supply.
- Caused by other determinants.
- Shown by shift of the entire supply curve.
Examples of Increase in Supply
- Better technology
- Lower cost
- Subsidy
Examples of Decrease in Supply
| Situation |
Answer |
| Price changes |
Movement |
| Cost or technology changes |
Shift |
ICAI MCQ Gold
- Movement = caused by price change.
- Shift = caused by non-price factors.
5. Elasticity of Supply
Definition
- Elasticity of supply means the responsiveness of supply to change in price.
Es = % change in Qs / % change in P
Types of Elasticity of Supply
| Type |
Meaning |
| Perfectly Elastic |
Infinite response |
| Elastic (>1) |
High response |
| Unitary (=1) |
Equal response |
| Inelastic (<1) |
Low response |
| Perfectly Inelastic |
No change |
Diagram Logic: Steeper supply curve means inelastic supply. Flatter supply curve means elastic supply.
6. Factors Affecting Elasticity of Supply
1. Nature of Goods
- Perishable goods → inelastic supply
- Durable goods → elastic supply
2. Time Period
- Very short run: Supply fixed, so perfectly inelastic
- Short run: Some flexibility exists
- Long run: Full flexibility, so supply becomes more elastic
3. Availability of Factors
- Easy availability of factors makes supply more elastic.
4. Level of Capacity Utilisation
- If idle capacity exists, supply is more elastic.
Very Important: As time period increases, elasticity of supply generally increases.
7. Market Supply
Definition
- Market supply means the sum of supply of all firms in the market.
- It is obtained by horizontal addition of individual supply curves.
8. Equilibrium
Definition
- Equilibrium occurs when demand equals supply.
Effects of Disequilibrium
- Excess demand → price rises
- Excess supply → price falls
Adjustment Mechanism
- Market forces move automatically towards equilibrium.
Final Quick Revision
Strict ICAI-based recall
- Supply = willingness + ability + time
- Supply is not stock
- Law of Supply = direct relationship
- Determinants = cost, technology, tax, related goods, expectations and more
- Movement = because of price
- Shift = because of other factors
- Elasticity = responsiveness of supply
- As time increases, elasticity usually increases
- Market supply = sum of all firms
- Equilibrium = demand equals supply
