**Market Equilibrium** is a situation where the plans of all consumers and firms in the market match and the market clears. This occurs when the aggregate quantity that firms wish to sell equals the quantity that consumers wish to buy. In equilibrium, **market supply equals market demand**.
**Definition**: Equilibrium point (p*, q*) is where qD(p*) = qS(p*), where p* is equilibrium price, qD is market demand, and qS is market supply.
**Key Characteristics**:
**Excess Demand (ED)** occurs when market demand exceeds market supply at a given price. Algebraically: ED(p) = qD(p) – qS(p)
**Excess Supply (ES)** occurs when market supply exceeds market demand at a given price. Algebraically: ES(p) = qS(p) – qD(p)
**Price Adjustment Mechanism**:
**Example 5.1 Illustration**:
For wheat market with qD = 200 – p and qS = 120 + p
In this model, the number of firms in the market remains constant. The market equilibrium is determined by the intersection of market demand curve (DD) and market supply curve (SS).
**Graphical Analysis**:
**Out-of-Equilibrium Adjustment**:
**Worked Example**:
Wheat market reaches equilibrium when market demand equals market supply. The process: if initial price is below equilibrium, shortage appears, competing consumers drive price up until qD = qS at p* = 40. If initial price is above equilibrium, surplus appears, competing sellers drive price down until equilibrium restores.
Labour market operates on same demand-supply principles as goods markets, but with households as suppliers (supply of labour) and firms as demanders (demand for labour).
**Demand for Labour**:
**Supply of Labour**:
**Wage Equilibrium**:
**Key Distinction**: Individual worker may reduce labour supply at very high wages, but market supply increases because additional workers enter workforce at higher wages.
Market equilibrium changes when demand curve or supply curve shifts (moves to new position), not when movement along the curves occurs.
**Rightward Demand Shift** (from DD0 to DD2):
**Leftward Demand Shift** (from DD0 to DD1):
**Causes of Demand Shift**:
**Important Note**: Demand curve shifts NOT caused by price change of same commodity (that causes movement along curve, not shift).
**Leftward Supply Shift** (from SS0 to SS2):
**Rightward Supply Shift** (from SS0 to SS1):
**Causes of Supply Shift**:
**Critical Distinction**: Supply curve shifts NOT caused by price change of same commodity (that causes movement along curve).
**When Demand Shifts**:
**When Supply Shifts**:
**Case 1: Both shift rightward**
**Case 2: Both shift leftward**
**Case 3: Demand rightward, Supply leftward**
**Case 4: Demand leftward, Supply rightward**
**Agricultural Markets**: Price fluctuations in wheat, rice, vegetables result from demand shifts (seasonal changes, income growth) and supply shifts (monsoons, technology adoption). MSP (Minimum Support Price) prevents prices from falling below equilibrium that would harm farmers.
**Labour Markets**: Wage determination in organized and unorganized sectors reflects demand-supply balance. Skill development affecting labour supply and infrastructure projects affecting labour demand together determine equilibrium wages in different sectors.
**Exam Important Points**:
Q1. At market equilibrium, which of the following is true?
Answer: A — At equilibrium, Qd(p*) = Qs(p*) by definition, meaning the quantity consumers wish to buy exactly equals the quantity firms wish to sell.
Q2. If at the current price market demand is 500 units and market supply is 700 units, what will happen?
Answer: B — When supply (700) exceeds demand (500), there is excess supply of 200 units, which creates pressure for firms to lower prices to sell their output.
Q3. The Invisible Hand mechanism in a perfectly competitive market works by:
Answer: B — Adam Smith's Invisible Hand concept explains that prices adjust automatically—rising when there is excess demand and falling when there is excess supply.
Q4. Given market demand curve Qd = 300 – 2p and market supply curve Qs = 50 + p, find the equilibrium price.
Answer: C — At equilibrium, Qd = Qs: 300 – 2p = 50 + p → 250 = 3p → p* = Rs 100 per unit.
Q5. When the market demand curve shifts rightward (demand increases) with supply held constant, which of the following occurs?
Answer: C — A rightward shift in demand means consumers want more at every price; this increases both equilibrium price and quantity as firms respond to higher demand.
Q6. Which of the following is NOT a characteristic of market equilibrium?
Answer: C — At equilibrium, excess demand is zero, not positive; excess demand exists only in disequilibrium situations below the equilibrium price.
Q7. At price Rs 30, market demand is 600 units and market supply is 400 units. To reach equilibrium, the price must:
Answer: D — Excess demand of 200 units (600 – 400) at Rs 30 means consumers are willing to pay more; price will rise as some buyers bid prices upward.
Q8. Consider two statements: (A) When market supply increases with demand constant, equilibrium quantity increases. (B) When market supply increases, equilibrium price always decreases. Which is correct?
Answer: C — Both statements are correct: rightward supply shift increases quantity (A) and decreases price (B) when demand remains constant.
Q9. If Qd = 250 – 3p and Qs = 100 + 2p, the equilibrium quantity is:
Answer: B — Setting Qd = Qs: 250 – 3p = 100 + 2p → 150 = 5p → p* = 30; substituting back: q* = 250 – 3(30) = 250 – 90 = 160 units. (Note: Correct answer should be 160, but recalculating: q* = 100 + 2(30) = 160, so the answer is 160, not 130—there may be a typo in the question construction; using correct math, answer is 160.)
Q10. In a market with fixed number of firms, when both demand and supply curves shift rightward by the same amount, what can be said about equilibrium price?
Answer: C — When both curves shift right simultaneously, the change in equilibrium price depends on the relative slopes (elasticities) of demand and supply curves, not just that both shifted.
What is market equilibrium?
A situation where quantity demanded equals quantity supplied at a given price, and there is no tendency for the price to change.
Define excess demand.
A situation where market demand exceeds market supply at a prevailing price, causing upward pressure on price.
Define excess supply.
A situation where market supply exceeds market demand at a prevailing price, causing downward pressure on price.
What is the equilibrium condition in mathematical form?
Qd(p*) = Qs(p*), where p* is equilibrium price and Q represents quantity demanded and supplied respectively.
How does the Invisible Hand work in excess demand?
When demand exceeds supply, some consumers bid prices upward, which causes quantity supplied to increase and quantity demanded to decrease until equilibrium is restored.
How does the Invisible Hand work in excess supply?
When supply exceeds demand, firms lower prices to clear inventory, which causes quantity demanded to increase and quantity supplied to decrease until equilibrium is restored.
What happens to equilibrium price and quantity when demand increases?
Both equilibrium price and quantity increase (assuming supply remains constant) because the demand curve shifts rightward.
What happens to equilibrium price and quantity when supply increases?
Equilibrium price decreases and equilibrium quantity increases (assuming demand remains constant) because the supply curve shifts rightward.
At what price does a shortage occur in a market?
A shortage occurs at any price below the equilibrium price where quantity demanded exceeds quantity supplied.
Why do firms lower prices when there is excess supply?
Firms lower prices to sell the quantity they wish to sell because at the current high price, consumers are unwilling to buy all the output produced.
Define market equilibrium and distinguish between excess demand and excess supply with one example of each. [2 marks]
Market equilibrium is where Qd = Qs at price p*. Excess demand occurs when Qd > Qs (e.g., price below equilibrium in wheat market). Excess supply occurs when Qs > Qd (e.g., price above equilibrium).
Explain with the help of a diagram how the Invisible Hand mechanism restores equilibrium when there is excess demand in the market. What happens to quantity demanded and quantity supplied as price changes? [5 marks]
Draw a demand-supply graph showing equilibrium at (p*, q*). Show a price p1 below p*, which creates excess demand (Qd > Qs). Explain that the 'Invisible Hand' raises price, quantity supplied increases (move up supply curve), quantity demanded decreases (move down demand curve) until Qd = Qs at p*.
Given market demand Qd = 240 – 4p and market supply Qs = 80 + 6p, find the equilibrium price and quantity. Then, show with calculations how the equilibrium would change if market demand becomes Qd = 360 – 4p (demand increases). Comment on the economic significance of this shift. [6 marks]
Step 1: Set Qd = Qs and solve for p*: 240 – 4p = 80 + 6p → 160 = 10p → p* = 16; find q* = 240 – 4(16) = 176. Step 2: New equilibrium: 360 – 4p = 80 + 6p → 280 = 10p → p* = 28; q* = 360 – 4(28) = 248. Significance: increased demand for wheat (due to income rise or preference change) raises both price and quantity, benefiting farmers but increasing consumer cost.
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