Theory of Supply: Factors, Elasticity, and Market Behavior

TAKEAWAYS:

• Supply is the quantity of goods/services producers are willing to sell at different prices.
• The law of supply states that as price rises, quantity supplied increases (and vice versa).
• Factors affecting supply include cost of production, technology, government policies, and producer expectations.
• Supply curves are upward-sloping, showing a direct relationship between price and quantity.
• Elasticity of supply measures how responsive quantity supplied is to price changes.
• Market equilibrium occurs where supply meets demand, but supply shifts can disrupt it.

---

What is Supply?

Supply refers to the quantity of a good or service that producers are willing and able to sell at a given price in a given time period. Unlike demand (which focuses on consumers), supply focuses on producers.

Key Idea:

• Producers supply goods/services to earn profit.
• They adjust how much they produce based on price and other factors.

---

The Law of Supply

The law of supply states:

Other things being equal, as the price of a good rises, the quantity supplied of that good also rises, and vice versa.

This means:

• If price increases, producers supply more.
• If price decreases, producers supply less.

Why?

• Higher prices mean more profit, so producers want to sell more.
• Lower prices mean less profit, so producers cut back production.

---

Supply Schedule and Supply Curve

Supply Schedule

A supply schedule is a table showing how much of a good producers are willing to supply at different prices.

Supply Curve

A supply curve is a graphical representation of the supply schedule. It is upward-sloping, showing a direct relationship between price and quantity supplied.

figure:line-chart: Supply Curve

Price (Rs.)
   ^
   |       /\
   |      /  \
   |     /    \
   |____/______\____> Quantity Supplied (units)

Key Points:

• The curve slopes upward because higher prices encourage more production.
• The curve shifts right (increase in supply) or left (decrease in supply) due to other factors (not just price).

---

Factors Affecting Supply

Supply is not just about price—many other factors influence how much producers supply. These are called non-price determinants of supply.

1. Cost of Production

• If input costs (raw materials, labor, energy) rise, supply decreases (curve shifts left).
• If costs fall, supply increases (curve shifts right).

Example:

• If the price of wheat increases, farmers grow more wheat → supply increases.
• If the price of fertilizer rises, farmers produce less → supply decreases.

2. Technology

• Better technology (e.g., automation, new machinery) lowers costs and increases supply.
• Older technology makes production costlier and reduces supply.

Example:

• Smartphones became cheaper and more available due to better manufacturing tech → supply increased.

3. Government Policies

• Subsidies (government payments to producers) → supply increases.
• Taxes (higher costs for producers) → supply decreases.
• Regulations (e.g., pollution laws) can reduce supply if they increase costs.

Example:

• Nepal’s government gives subsidies to farmers → more rice is produced.

4. Number of Producers

• More producers in the market → more supply.
• Fewer producers → less supply.

Example:

• If new coffee farms open, total coffee supply increases.

5. Producer Expectations

• If producers expect future prices to rise, they may supply less now to sell later.
• If they expect lower future prices, they may supply more now.

Example:

• If farmers think tomorrow’s wheat price will be higher, they may store wheat today instead of selling.

6. Natural Conditions (for Agricultural Goods)

• Good weather → more supply.
• Bad weather (drought, floods) → less supply.

Example:

• If monsoon fails, rice production drops → supply decreases.

---

Changes in Supply vs. Changes in Quantity Supplied

figure:mermaid
flowchart TD
    A["Price Change"] -->|Rise/Fall| B["Movement along supply curve\n(Quantity Supplied changes)"]
    C["Non-Price Factors\n(Cost, Tech, Govt. Policy, etc.)"] -->|Change| D["Shift of supply curve\n(Supply changes)"]

---

Elasticity of Supply

Elasticity of supply measures how responsive the quantity supplied is to a change in price.

Formula:

$$E_s=\frac{\%\text{ Change in Quantity Supplied}}{\%\text{ Change in Price}}$$

Types of Elasticity:

1. Perfectly Elastic Supply

   • Supply curve is horizontal (infinite elasticity).
   • Producers supply any quantity at the same price.
   • Example: Agricultural goods (if farmers can easily adjust production).

2. Perfectly Inelastic Supply

   • Supply curve is vertical (zero elasticity).
   • Quantity supplied does not change with price.
   • Example: Artworks, vintage items (limited supply).

3. Unitary Elastic Supply

   • % change in quantity = % change in price.
   • Supply curve is straight line through origin.

4. Relatively Elastic Supply

   • % change in quantity > % change in price.
   • Example: Manufactured goods (easier to adjust production).

5. Relatively Inelastic Supply

   • % change in quantity < % change in price.
   • Example: Natural resources (hard to increase supply quickly).

figure:line-chart: Elasticity of Supply

Price (Rs.)
   ^
   |       ________ (Perfectly Elastic)
   |      /
   |     /
   |____/______ (Unitary Elastic)
   |     \
   |      \
   |_______\______ (Perfectly Inelastic)
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |
   |