Supply is the quantity of goods and services that producers are willing and able to offer at different price levels during a given period.
## Core concept
Supply represents the stock of output available for sale at various prices. Unlike demand (buyer's perspective), supply reflects the seller's behaviour—how much producers will produce and sell at different market prices.
Key distinction from Demand: - Demand: What buyers want to purchase - Supply: What sellers want to sell
Supply is influenced by: - Price of the good - Cost of production (raw materials, labour, technology) - Number of sellers in the market - Expectations about future prices - Government policies and taxes
## Law of Supply
The fundamental principle states: As price rises, quantity supplied increases; as price falls, quantity supplied decreases—all else being equal (ceteris paribus).
This positive relationship between price and quantity supplied occurs because: - Higher prices encourage producers to allocate more resources to that good - Profit margins improve, incentivizing increased production - Marginal producers (operating at lower profit margins) become profitable
Supply Schedule and Curve: A supply schedule is a table showing price–quantity supplied pairs. When plotted, it forms the supply curve—typically upward-sloping (from left to right).
| Price (₹) | Qty Supplied (units) | |-----------|----------------------| | 10 | 100 | | 15 | 150 | | 20 | 200 |
## Determinants of Supply (Shift Factors)
Changes in these factors shift the entire supply curve, not movement along it:
- Technology: Better technology lowers costs → increases supply (rightward shift)
- Input costs: Rise in wages or raw material prices → decreases supply (leftward shift)
- Number of sellers: More producers → supply increases
- Expected future prices: If prices expected to rise, supply decreases today (sellers hold inventory)
- Government policy: Subsidies increase supply; taxes decrease it
- Natural conditions: Drought/floods affect agricultural supply
## Movement vs Shift
Movement along the supply curve: Only price of the good changes → reflects Law of Supply
Shift of the supply curve: Any other determinant changes → entire curve moves (increase = rightward; decrease = leftward)
## Common exam applications
- Problem: "Price of cotton rises from ₹5,000 to ₹6,000 per bale. Quantity supplied increases from 1,000 to 1,200 bales."
- - Answer: Movement along the curve (Law of Supply operates)
2. Problem: "New weaving technology reduces production costs. What happens to cotton supply?" - Answer: Supply increases (rightward shift of curve) because profitability improves
3. Problem: "Government imposes excise duty on steel. How does supply react?" - Answer: Supply decreases (leftward shift) because effective profit margin shrinks for producers
4. Agricultural supply: Monsoon failure → input scarcity → supply falls (shift left)
## Common mistakes
- Confusing movement with shift: A price change causes movement *along* the curve, not a shift *of* the curve
- Ignoring ceteris paribus: When applying the Law of Supply, assume all other factors remain constant
- Reversing the relationship: Supply slopes upward (not downward like demand)
- Mixing supply determinants with demand determinants: Cost of production shifts supply; consumer income shifts demand
- Supply vs Quantity Supplied: Supply (entire schedule/curve) differs from quantity supplied (single point on curve)
Exam tip: Always specify whether you're discussing movement (price-driven) or shift (other factors). Use diagrams to illustrate — examiners reward clear visual representation.