Teachers recommend using Class 9 SST Notes and NCERT Class 9 SST Chapter 9 The Price Puzzle What Drives the Market Notes for quick revision before tests.
Class 9 The Price Puzzle What Drives the Market Notes
Class 9 SST Chapter 9 The Price Puzzle What Drives the Market Notes
Demand and Supply, Deviations
Every day, people buy and sell goods and services. The price of tomatoes can rise after heavy rain damages crops.
The price of umbrellas increases during the monsoon. A cinema ticket costs more on weekends than on weekdays.
These changes are not random. In most cases, .prices change because of the way buyers and sellers respond to market conditions.
Economics explains these changes using two simple ideas: demand and supply.
What is demand: Demand refers to the quantity of a commodity that a consumer is willing and able to buy at a particular price during a given period of time.
The law of demand states that, keeping all other factors constant (ceteris paribus), there is an inverse relationship between price and quantity demanded.
Law is based on following assumptions: There is no change in the price of related goods. There is no change in the income of consumers. Tastes and preferences remain constant. There are no expectations of price change in the future.
What is supply: Supply is the quantity of a commodity that a producer is willing and able to sell at a particular price during a given period of time.
The law of supply states that, keeping all other factors constant, (ceteris paribus), there is a direct relationship between price and quantity supplied.
Assumptions of the Law of Supply: There is no change in the price of related goods. There is no change in the prices of inputs. The state of technology remains constant. There is no change in the government policy. There are no changes in the goals of the firms.
Demand and supply are the fundamental forces that determine price in a market.
These laws explain the behaviour of consumers and producers in response to changes in price.
Class 9 SST Chapter 9 Notes – The Price Puzzle What Drives the Market Notes Class 9
Do these laws always hold true?
While the laws of demand and supply explain general market behaviour, they may not always apply in real- life situations. In certain cases, such as essential goods (like salt, life-saving medicines), perishable goods (like vegetables), or when people expect prices to rise or fall in the future, consumers and producers may not respond to price changes in the usual way.
These situations are known as deviations from the laws.
Law of Demand
The law of demand explains that, keeping other factors constant, an increase in the price of a good leads to a decrease in itfe quantity demanded. This inverse relationship is due to:
Substitution Effect: Consumers shift to relatively cheaper substitutes when the price of a good rises. For example, when the price for coffee increases, people may shift to tea leading to a rising demand for tea.
Income Effect: When prices rise, the actual purchasing power of consumers decreases. For example, if the price of milk increases, a family may buy less milk because their income cannot afford the usual quantity.
Diminishing Marginal Utility: As a consumer buys more units of a good, the additional satisfaction from each extra unit decreases. So consumers are less willing to pay a higher price for more units of the same good. For example, the first slice of pizza gives more satisfaction than the fourth, so consumers are not willing to pay the same price for additional units.
Consumer Behaviour: Consumers tend to maximise satisfaction by avoiding higher-priced goods. For example, when the price of branded shoes increases, consumers may delay the purchase or choose cheaper alternatives.
Demand Schedule: Inverse Relationship between Price and Quantity Demanded
| Price of Good (₹) | Quantity Demanded (Units) | Relationship |
| 10 | 100 | As price rises ↑ |
| 20 | 80 | Demand falls ↓ |
| 30 | 60 | |
| 40 | 40 | |
| 50 | 20 |
Demand Curve — What the Graph Shows
The graph shows the relationship between the price of a good and the quantity demanded. Price is shown on the vertical (Y) axis, while quantity demanded is shown on the horizontal (X) axis.
The demand curve slopes downward from left to right, indicating an inverse relationship between price and quantity demanded.
As the price rises from ₹10 to ₹50, the quantity demanded falls from 100 units to 20 units. This illustrates the Law of Demand, which states that, other things remaining constant, quantity demanded varies inversely with price.
A movement along the demand curve occurs due to a change in the price of the good, while a shift of the demand curve occurs due to changes in other factors such as income, tastes and preferences, or prices of related goods.
Individual Demand and Market Demand
Individual demand refers to the quantity of a good that a single consumer is willing and able to buy at various prices. Each consumer makes decisions based on their income, taste, and need.
Market demand is the total demand of all consumers for a good at a given price. It is obtained by adding up individual demands. Producers and policymakers focus mainly on market demand rather than individual demand.
Factors Affecting Demand
| Factor | Effect on Demand |
| Income of consumers | Higher income → demand rises; lower income → demand falls |
| Tastes and preferences | If a product becomes fashionable, demand increases |
| Prices of related goods | If the price of a substitute rises, demand for the original good rises |
| Expectations about future prices | If prices are expected to rise, consumers buy more now |
| Size of population | Larger population → higher market demand |
Shifts in Demand
Demand can change even when the price of the good stays the same. When this happens, the demand curve shifts.
If demand increases, the demand curve shifts to the right. At the same price, consumers want to buy more than before.
If demand decreases, the demand curve shifts to the left. At the same price, consumers want to buy less than before.
Common causes: change in income, change in tastes, change in prices of related goods, change in expectations, change in population size.
Law of Supply
The law of supply states that, other factors remaining constant, an increase in price leads to an increase in quantity supplied. This direct relationship exists because:
Profit Motive: Higher prices increase profit margins for producers. With rising prices, producers increase their production to attain higher profits.
Expansion of Production: With rising prices, firms are encouraged to increase output to earn higher revenue.
Entry of New Firms: Higher prices attract new producers into the market, which increases the supply in the market.
Supply Schedule: Direct Relationship between Price and Quantity Supplied
| Price of Good (₹) | Quantity Supplied (Units) | Relationship |
| 10 | 20 | As price rises ↑ |
| 20 | 40 | Supply rises ↓ |
| 30 | 60 | |
| 40 | 80 | |
| 50 | 100 |
Supply Curve — What the Graph Shows
The graph shows the relationship between the price of a good and the quantity supplied. Price is shown on the vertical (Y) axis, while quantity supplied is shown on the horizontal (X) axis.
The supply curve slopes upward from left to right, indicating a direct relationship between price and quantity supplied.
As the price rises from ₹10 to ₹50, the quantity supplied increases from 20 units to 100 units. This happens because higher prices encourage producers to supply more goods in the market.
A change in price causes movement along the supply curve. Changes in factors such as production costs, technology, or government policies can shift the entire supply curve.
Deviation from the Laws of Demand and Supply
Meaning of Deviation
In real life, demand and supply may not always follow the usual relationship with price. Such situations are called deviations from the laws of demand and supply.
Normally:
- Demand decreases when price increases.
- Supply increases when price increases.
However, in some cases, this may not happen.
Factors Causing Deviations
Deviations occur due to:
- Nature of goods (necessities or luxury goods)
- Urgency of need
- Expectations about future prices
- Nature of the product (perishable goods)
1. Necessities
Necessities such as salt, food grains and life-saving medicines are goods people cannot do without. When their price rises, demand does not fall much, since consumption cannot easily be reduced.
2. Luxury / Status Goods
Status goods are luxury goods that people buy not only for their usefulness but also for the prestige and social status associated with owning them, such as designer handbags, luxury cars, or premium watches. In some cases, a rise in price makes these goods appear more exclusive and desirable, leading to an increase in demand. This phenomenon is known as the Veblen effect and is a recognised deviation from the law of demand.
3. Perishable Goods
Perishable goods such as fresh fish, milk, vegetables, and baked items spoil quickly. Sellers face time pressure to sell these goods. A seller may lower prices near the end of the day to avoid waste. This can cause unusual price behaviour — supply may increase even when prices fall, which is a deviation from the law of supply.
4. Expectations of Future Prices
If prices are expected to rise in the future, consumers may buy more even at higher prices, while producers may reduce current supply to sell later at higher prices.
| Situation | What happens | Why |
| Necessities | Demand does not fall much | Essential needs |
| Luxury goods | Demand may increase with price | Status value |
| Perishable goods | Supply may increase even at low price | Avoid losses |
| Expectations | Demand/supply
changes |
Future price anticipation |
Individual Supply and Market Supply
Individual supply refers to the quantity of a good that one producer is willing to sell at different prices. Each producer makes decisions based on costs, resources, and expected profit.
Market supply is the total supply of all producers in the market at a given price. It is obtained by adding individual
Factors Affecting Supply
| Factor | Effect on Supply |
| Cost of production | Higher costs → supply falls; lower costs → supply rises |
| Technology | Better technology → production becomes efficient → supply rises |
| Number of producers | More producers → market supply rises |
| Expectations about future prices | If prices expected to rise, producers may hold back current supply |
| Natural
conditions |
Good weather → agricultural supply rises; drought → supply falls |
| Government
policies |
Taxes increase costs → supply falls; subsidies reduce costs → supply rises |
Shifts in Supply
Supply can change even when the price of the good stays the same. When this happens, the supply curve shifts.
- If supply increases, the supply curve shifts to the right. At the same price, producers supply more than before.
- If supply decreases, the supply curve shifts to the left. At the same price, producers supply less than before.
Common causes: change in cost of production, change in technology, change in number of sellers, change in natural conditions, change in government policy, change in expectations about future prices.
Important distinction:
- A change in quantity demanded/supplied happens when the price of the good changes — the consumer or producer moves along the same curve.
- A change in demand/supply happens when something other than price changes — the entire curve shifts.
Enrichment Information
The concepts of demand and supply form the foundation of microeconomics. They are widely used to analyse market trends, price fluctuations, business strategies and government policies.
Quick Summary
| Concept | Key Idea | Example |
| Law of Demand | Price ↑ → Demand ↓ | Higher petrol prices reduce usage |
| Law of Supply | Price ↑ → Supply ↑ | Farmers grow more when crop prices rise |
| Movement along Curve | Change due to price | Price fall → Demand increases |
| Shift of Curve | Change due to other factors | Income rise → Demand increases |
| Necessities | Demand does not fall much when price rises | Electricity, water |
| Luxury Goods | Demand may increase with price (status) | Branded products |
| Perishable Goods | Supply may not decrease even when price falls | Fruits, vegetables |
| Expectations | Future price expectations affect demand/ supply | Hoarding when prices expected to rise |
Market Equilibrium and Market Outcomes
- Market equilibrium occurs when quantity demanded equals quantity supplied.
- Equilibrium price is the price at which demand and supply intersect.
- When equilibrium is disturbed, it leads to a surplus or shortage.
- Changes in demand or supply result in a shift in the equilibrium price and quantity.
Market Equilibrium
Market equilibrium is the situation in which the quantity demanded equals the quantity supplied at a particular price. At this point, there is no excess demand or excess supply; the market is in balance and there is no tendency for the price to change.
Market Schedule— Equilibrium, Surplus and Shortage
| Price (₹) | Qty Demanded | Qty Supplied | Market Condition |
| 10 | 100 | 20 | Shortage (Demand > Supply) |
| 20 | 80 | 40 | Shortage |
| 30 | 60 | 60 | ✓ EQUILIBRIUM |
| 40 | 40 | 80 | Surplus (Supply > Demand) |
| 50 | 20 | 100 | Surplus |
Graph: How Surplus Appears on a Demand-Supply Diagram
The downward sloping curve represents demand.
The upward sloping curve represents supply.
The point where the demand and supply curves intersect is called equilibrium.
Here:
Price = ₹30
Quantity = 60 units
At this point, demand = supply
At prices above ₹ 30 say, ₹ 40
Quantity supplied (80 units) > Quantity demanded (40 units)
Producers supply more than consumers are willing to buy.
This creates a surplus (excess supply).
The gap between the supply and demand curves above the equilibrium price shows the surplus and represents unsold goods in the market.
Sellers are unable to sell all goods: To attract buyers, they reduce prices and the prices move back toward equilibrium.
Graph: How Shortage Appears on a Demand-Supply Diagram
The equilibrium price is ₹ 30 and equilibrium quantity is 60 units, where demand and supply intersect.
At price below ₹ 30, say ₹ 20,
Quantity supplied < Quantity demanded
Consumers want to buy more, but producers are willing to supply less.
This creates shortage as shown by the shaded region. As a result, there is an upward pressure on the prices and they tend to move back to the equilibrium.
Changes in Market Conditions
Increase in demand: Raises the equilibrium price and quantity.
Decrease in demand: Lowers the equilibrium price and quantity.
Increase in supply: Lowers price but increases quantity.
Decrease in supply: Raises price but reduces quantity.
Memory Box: Equilibrium, Surplus and Shortage
| Situation | Demand vs Supply | Result | Price Movement |
| Equilibrium | Demand = Supply | Balanced Market |
No change |
| Surplus | Supply > Demand | Excess
goods |
Price ↓ |
| Shortage | Demand > Supply | Excess
demand |
Price ↑ |
Quick Rule: Above equilibrium → Surplus → Price falls | Below equilibrium → Shortage → Price rises
Effect of Changes in Demand and Supply on Equilibrium
|
Change |
Effect on Equilibrium Price |
Effect on Equilibrium Quantity |
| Demand increases | Rises | Rises |
| Demand decreases | Falls | Falls |
| Supply increases | Falls | Rises |
| Supply decreases | Rises | Falls |
Enrichment Information
Market equilibrium plays a crucial role in determining prices in real-world markets. It helps businesses plan production, guides consumers in decision-making, and assists governments in understanding market behaviour.
Role of Government in the Economy
Sometimes, markets alone cannot achieve desirable outcomes for society. In such situations, the government intervenes to protect consumers, promote social welfare and improve market efficiency.
- Price ceilings are maximum prices fixed by the government to protect consumers.
- Price ceilings often lead to shortages and black markets.
- Public goods are non-excludable and non-rival in nature.
Price Ceilings
A price ceiling is the maximum price fixed by the government, usually below the equilibrium price, to make essential goods affordable.The government imposes a price ceiling when the equilibrium price is too high and out of reach for many people.The government uses this option for essential commodities, such as food and medicines.
Price Ceiling: Market Schedule Example (Equilibrium Price = ₹ 30, Ceiling at ₹ 20)
| Market Situation | Price |
Qty Demanded |
Qty Supplied | Outcome |
| Free Market Equilibrium | ₹ 30 | 60 units | 60 units | Balanced — no surplus or shortage |
| After Price Ceiling Set | ₹ 20 | 80 units | 40 units | Shortage of 40 units → Black market risk |
Graph: How Price Ceiling Creates Shortage.
The graph shows the effect of a price ceiling on a market.
Equilibrium
The demand curve (D) slopes downward and the supply curve (S) slopes upward.
They intersect at point E, which is the equilibrium point where:
Price = ₹ 30
Quantity = 60 units
Price Ceiling
The government fixes the price at₹ 20, which is below equilibrium price.
This is shown by a horizontal line at ₹ 20.
Effect on Demand and Supply
At ₹ 20:
Quantity Demanded increases to 80 units as more people want to buy at lower price.
Quantity Supplied decreases to 40 units as producers supply less due to lower profit.
Shortage
Since demand (80) > supply (40), a shortage of 40 units arises which is shown by the shaded area between 40 and 80 units.
This shortage leads to risk of Black Market.
Shortages and Black Markets
When prices are fixed below equilibrium, the demand increases while the supply decreases. This creates a shortage, as the quantity demanded exceeds the quantity supplied. As a result, black markets may emerge, where goods are sold illegally at higher prices.
Market Failures
Market failure occurs when the free market fails to allocate resources efficiently, resulting in overproduction or underproduction of goods and a loss of overall social welfare.
Causes include:
Externalities: Effects of production/consumption on third parties who are not directly involved. For example, pollution from nearby factories harms the residents.
Negative externalities cause harm to others not involved in a transaction. Example: A factory discharges waste into a river, harming fishermen and residents downstream. Since the factory does not bear this cost, it produces too much — leading to overproduction relative to the socially desirable level.
Positive externalities provide benefits to others not involved in a transaction. Example: When a person gets vaccinated, nearby people also benefit because the disease is less likely to spread. However, since these wider benefits are not reflected in private decisions, the market may provide too little vaccination — leading to underproduction relative to the socially desirable level. In both cases, the market outcome differs from what is best for society because the price signal is incomplete. This justifies government intervention through taxes (for negative externalities) and subsidies (for positive externalities).
Information asymmetry: A situation where one party has ‘more information than the other, leading to an unfair or inefficient decision.
Public goods: Public goods are those goods that are available for use by everyone. These goods are non-excludable and non-rival. They are not efficiently provided by markets.
Public Goods
Non-excludable: People cannot be prevented from using them.
Non-rival: One person’s use does not reduce availability for others.
Examples: street lighting, national defence, public parks.
Memory Box: Price Control & Market Failure
| Concept | Key Idea | Result |
| Price Ceiling | Price fixed below equilibrium | Shortage |
| Shortage | Demand > Supply | Price pressure ↑ |
| Black Market | Illegal selling | Higher prices |
| Public Goods | Non-excludable & non-rival | Government
provision |
Price Floor
A price floor is the minimum price set by the government for a good or service. Sellers are not allowed to sell below this price. It is usually introduced to protect producers or workers from very low market prices.
Purpose of Price Floors
- To protect farmers and producers from falling market prices that may not cover their costs of production.
- To ensure workers receive a minimum wage that allows them to maintain a basic standard of living.
Examples of Price Floors:
Minimum Support Price (MSP): The government fixes a minimum price for crops such as wheat, rice, and sugarcane to protect farmers from falling market prices. Even if the market price falls, the government guarantees to buy crops at the MSP.
Minimum Wage: The government sets the lowest wage that employers must pay workers, ensuring they are not exploited with very low pay.
Effects of a Price Floor
When a price floor is set above the equilibrium price, it leads to:
Excess supply (surplus): Producers supply more than consumers are willing to buy at the higher price.
Unsold stock: Goods may remain unsold because demand is lower at the higher price.
Government intervention: The government may need to purchase the excess supply, as it does under the MSP scheme for agricultural goods.
Just like price ceilings create shortages, price floors create surpluses, because prices are kept higher than the market equilibrium level.
Why Markets Fail
Markets may fail due to several reasons:
Inequality in income and access: Some people may not be able to afford basic goods, even if the market is functioning efficiently. This leads to unequal outcomes in healthcare, education, and housing.
Lack of information: Consumers or producers may not have complete or accurate information about products, risks, or consequences. For example, people may unknowingly buy harmful products, or firms may ignore environmental damage. This is called information asymmetry.
Focus on profit over social welfare: Markets focus mainly on profit, not on social concerns. Issues like pollution, deforestation, and public health may be ignored because firms find it costly to address them. These are called externalities.
Certain essential goods are not profitable: Some essential gpods are not supplied by private firms because they capnot charge users or earn profit from them. These are called public goods.
Role of Government in Correcting Market Failure
The government may intervene in various ways to correct market failures:
(i) Taxes: Impose taxes on harmful activities such as pollution and tobacco use to reduce negative externalities and make producers bear the true social cost.
(ii) Subsidies: Encourage beneficial activities such as education and healthcare where positive externalities exist but the market underproduces.
(iii) Regulation: Enforce laws and safety standards to ensure fair practices and prevent harmful production.
(iv) Public provision: Directly provide essential goods and services like roads, defence, and street lighting that private firms will not supply.
(v) Information rules: Ensure consumers receive accurate information through labelling laws, safety standards, and consumer protection regulations.
Government intervention does not eliminate markets: it complements them by making them more efficient, fair, and socially responsible.