Demand Basics — the quantity of goods or services consumers are willing and able to purchase at different price levels in a given period.
## Core concept
Demand represents effective desire — not mere wish, but backed by purchasing power and willingness to pay. It is expressed as a schedule or curve showing the inverse relationship between price and quantity demanded, holding all other factors constant.
Key characteristics: - Two-dimensional relationship: Price of the good and quantity demanded - Ceteris paribus assumption: All other variables (income, taste, prices of related goods) remain constant - Time period: Demand is always measured for a specific time interval (daily, weekly, monthly) - Market demand: Sum of individual demands of all consumers at each price level
## Formula / rule
Demand Function: Qd = f(P, Y, Pr, T, E, ...)
Where: - Qd = Quantity demanded - P = Price of the good (main determinant) - Y = Consumer income - Pr = Price of related goods - T = Taste and preferences - E = Expectations - Other factors like population, advertisements, seasons
Basic Demand Schedule (Hypothetical Example):
| Price (₹) | Quantity Demanded (units) | |-----------|---------------------------| | 100 | 50 | | 80 | 70 | | 60 | 100 | | 40 | 140 |
The negative slope illustrates the Law of Demand: As price increases, quantity demanded decreases (and vice versa), assuming income and preferences remain unchanged.
## Common exam applications
1. Movement along demand curve vs. shift in demand curve: - Movement along: Caused by change in price of the good itself — demand curve remains fixed, only quantity demanded changes - Shift in demand curve: Caused by change in other determinants (income, taste, related goods' prices) — entire curve moves
2. Identifying demand shifters (Intermediate theory but tested at Foundation): - Income increase → demand shifts right (normal goods); shifts left (inferior goods) - Change in taste → shifts curve - Price of substitutes increases → demand for the good increases (rightward shift) - Price of complements increases → demand for the good decreases (leftward shift)
3. Practical scenario question: A fall in the price of smartphones from ₹50,000 to ₹40,000 results in quantity demanded increasing from 10,000 to 15,000 units. This is a movement along the demand curve (not a shift), illustrating the Law of Demand.
## Common mistakes
- Confusing demand with supply: Demand is quantity consumers want to buy; supply is quantity producers want to sell
- Mixing up shift and movement: Price changes cause movements; other factors cause shifts
- Ignoring "willing and able": Demand must include both desire AND purchasing capacity
- Overlooking time dimension: Demand at ₹50 per unit per month is different from per week
- Assuming demand curve is always downward-sloping: While typical, Giffen goods and Veblen goods are rare exceptions not heavily tested at Foundation level
## Quick check for exams
- Define demand with at least two characteristics
- Always mention price and quantity relationship in answers
- Distinguish demand from quantity demanded
- Recognize that only price changes cause movement along the curve
- Remember: Law of Demand = negative relationship between P and Qd