2.1 Demand and Supply Curves

Chapter 2.1: Demand and Supply Curves – Detailed Revision Notes

Introduction to Demand and Supply

Demand and supply are the foundational concepts of microeconomics, representing the behavior of buyers and sellers in a market. The interaction between demand and supply determines the price and quantity of goods and services traded. These concepts are crucial to understanding how markets function, reach equilibrium, and respond to various internal and external changes.

2.1.1 Effective Demand

Effective demand refers to the quantity of a good or service that consumers are both willing and able to purchase at various price levels, during a specific period, ceteris paribus (all other factors held constant).

• Notional Demand: Desires or wants without purchasing power.
• Effective Demand: Actual purchasing behavior backed by money.
• Example: Many people may want a luxury car (notional demand), but only a few can afford it (effective demand).

To count in market analysis, demand must be effective.

2.1.2 Individual and Market Demand and Supply

Individual Demand: The quantity of a good or service a single consumer is willing and able to buy at different prices over a specific period.

Market Demand: The total quantity of a good or service demanded by all consumers in the market. It is derived by summing all individual demands.

Individual Supply: The amount of a good a single producer is willing and able to sell at various prices.

Market Supply: The total quantity supplied by all producers in the market. It is the horizontal summation of all individual supply curves.

Graphically:

• Demand curves generally slope downward (law of demand).
• Supply curves slope upward (law of supply).

2.1.3 Determinants of Demand

These are non-price factors that affect demand and can shift the demand curve:

1. Price of the Good (movement along the curve):

Inverse relationship: As price increases, demand decreases.

2. Income of the Consumer:

• Normal goods: Demand increases with income.
• Inferior goods: Demand decreases as income rises.

3. Tastes and Preferences:

• Influenced by fashion, advertising, trends, culture, etc.
• Positive changes increase demand.

4. Price of Related Goods:

• Substitute Goods: An increase in the price of one increases demand for its substitute (e.g., tea vs. coffee).
• Complementary Goods: An increase in the price of one reduces demand for its complement (e.g., printer and ink).

5. Future Price Expectations:

• If consumers expect prices to rise, they may buy more now, increasing current demand.

6. Seasonal Factors:

• Certain goods are demanded more in specific seasons (e.g., heaters in winter, umbrellas in monsoon).

2.1.4 Determinants of Supply

These are factors other than price that influence the supply of a good or service:

1. Cost of Production:

• • Increase in input costs (wages, raw materials) reduces supply.
  • A decrease in costs increases supply.

2. Technology:

• Advances improve productivity, increasing supply.

3. Taxes and Subsidies:

• Taxes (e.g., VAT) increase production costs and reduce supply.
• Subsidies reduce costs and increase supplyWeather and Natural Conditions:
  • Especially relevant for agricultural goods.
  • Bad weather reduces supply, good weather enhances it.

4. Prices of Other Goods:

• If another product becomes more profitable, producers may switch, reducing supply of the current good.

5. Future Expectations:

• If producers expect prices to rise, they may withhold supply now.

2.1.5 Causes of a Shift in the Demand Curve

A shift in the demand curve means that at every price level, the quantity demanded changes due to non-price determinants:

• Rightward Shift (Increase in Demand):
• Rise in income (for normal goods)
• Increased preference for the good
• Decrease in price of complementary goods
• Increase in price of substitute goods
• Positive future price expectations
• Population growth
• Leftward Shift (Decrease in Demand):
• Fall in income (for normal goods)
• Loss of preference
• Increase in price of complementary goods
• Decrease in price of substitute goods
• Negative future price expectations

Graphically, the entire demand curve moves to the right or left.

2.1.6 Causes of a Shift in the Supply Curve

A shift in the supply curve indicates a change in supply at every price point due to factors other than the product’s own price:

• Rightward Shift (Increase in Supply):
• Decrease in cost of production
• Technological advancements
• Introduction/increase of subsidies
• Favorable weather conditions
• Decrease in taxes
• Leftward Shift (Decrease in Supply):
• Increase in production costs
• Withdrawal of subsidies
• Natural disasters or poor weather
• Imposition of new taxes
• Depletion of resources

Graphically, the supply curve shifts to the right or left.

2.1.7 Shift vs. Movement Along the Demand and Supply Curves

Understanding the difference between shifts and movements is crucial:

• Movement Along the Curve:
• Caused by a change in the price of the good itself.
• On the demand curve, a price fall leads to an extension (movement down the curve), and a price rise leads to a contraction (movement up).
• On the supply curve, a price rise leads to an extension (movement up), and a price fall leads to a contraction (movement down).
• Shift of the Curve:
• Caused by non-price factors (income, preferences, costs, technology, etc.).
• A shift means the entire curve moves right (increase) or left (decrease).
• Indicates a change in demand or supply at every price level.

Example:

• A fall in the price of petrol causes a movement along the supply curve (increase in quantity supplied).
• A government subsidy causes a shift in the supply curve (increase in supply).

Conclusion

Understanding demand and supply curves and the factors that influence their movement or shift is essential in analyzing how markets allocate resources and set prices. These fundamental tools help economists and businesses predict responses to policy changes, external shocks, or internal developments in the market.