Desire
The consumer wants the product.
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Law of Demand
Why might you buy more mangoes when their price falls, but purchase fewer when they become expensive? The law of demand explains the usual relationship between a product's price and the quantity consumers are willing and able to buy.
This principle is fundamental to understanding shopping decisions, business pricing, market behaviour, and how consumers respond to price changes.
The basic relationship
Assuming other factors remain unchanged
Price rises
Quantity demanded generally falls.
Price falls
Quantity demanded generally rises.
This is the usual inverse relationship described by the law, not a guarantee that every real-world price change produces the same result.
1. What Is the Law of Demand?
The law of demand states that, other things remaining equal, quantity demanded of a goods generally increases when its price decreases and decreases when its price increases. Economists describe this as an inverse relationship between price and quantity demanded.
The phrase other things remaining equal is important. It means we are considering a change in the product's own price while assuming that other important influences—such as consumer income, preferences, prices of related goods , and expectations—remain unchanged.
The law in one sentence
When the price of a product falls, consumers generally want to buy more of it; when the price rises, they generally want to buy less, provided other relevant factors remain the same.
Demand is more than just wanting a product
In economics, demand means that consumers are willing and able to purchase a product at different prices during a specified period. Someone may want an expensive car, for example, but without the ability or willingness to pay for it, that desire does not necessarily count as effective market demand.
Ability to pay
The consumer has the resources to buy it.
Willingness to buy
The consumer is prepared to make the purchase at the relevant price.
2. Why Does the Law of Demand Usually Work?
A price change can influence consumers in several ways. These explanations help us understand why a lower price often leads to higher quantity demanded.
Purchasing power
When a product becomes cheaper, the same budget can buy more units. A family with ₹200 to spend on fruit may be able to buy more oranges if the price per kilogram falls.
Substitution
If one product becomes cheaper relative to a similar product, consumers may switch toward it. If the price of one brand of detergent falls while competing brands remain expensive, some shoppers may choose the discounted brand.
More potential buyers
A lower price may make a product affordable to people who could not justify buying it at the previous price. More consumers may enter the market at the lower price.
The value of additional units
A consumer may be willing to buy the first unit at a relatively high price but only buy extra units if the price is lower. This is one way the law connects with consumer-choice theory.
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3. Demand Schedule: A Numerical Example
A demand schedule is a table showing the quantities a consumer is willing and able to buy at different prices during a given period. Imagine a student buying cups of a favourite drink over a day. The table below is hypothetical and illustrates the law of demand.
| Price per cup (₹) | Quantity demanded (cups) | Relationship |
|---|---|---|
| 100 | 1 | Highest listed price |
| 80 | 2 | Lower price, more units |
| 60 | 3 | Lower price, more units |
| 40 | 4 | Lower price, more units |
| 20 | 5 | Lowest listed price |
In this illustration, when the price falls from ₹100 to ₹20 per cup, quantity demanded increases from one cup to five cups. The example does not predict how real customers will behave; actual responses depend on preferences, income, alternatives, and other factors.
Price increases
In the example, moving from ₹20 toward ₹100 corresponds to buying fewer cups.
Price decreases
Moving from ₹100 toward ₹20 corresponds to buying more cups.
4. Demand Curve: A Visual Explanation
A demand curve is a graph showing the relationship between price and quantity demanded. In the conventional graph, price is shown on the vertical axis and quantity demanded on the horizontal axis. The usual demand curve slopes downward from left to right.
Demand curveIllustrative data based on the schedule above
The plotted points illustrate a downward-sloping demand curve. The spacing is conceptual rather than a calibrated scale for a real product.
How to read the curve
- Start at a point representing a particular price and quantity.
- Move down the curve to represent a lower price and higher quantity demanded.
- Move up the curve to represent a higher price and lower quantity demanded.
- The curve describes a relationship; it does not by itself explain every reason demand changes.
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5. Interesting Real-Life Examples
The law of demand becomes easier to understand when you connect it with everyday shopping decisions. The following examples are illustrations of the usual pattern, assuming other relevant factors remain unchanged.
Example 1: Tea at a local shop
A small change in price may affect repeat purchases
Imagine a student buys tea between classes. If a cup costs ₹20, the student may buy one cup. If the price falls to ₹12, the student may be more willing to buy an additional cup or visit more often, depending on their budget and preferences.
Economic lesson: A lower price can make an extra purchase more attractive. It does not guarantee that every customer will buy more.
Example 2: Mangoes during the season
Consumers may buy more when the price becomes affordable
During mango season, suppose a family finds that mangoes become cheaper at the market. The family may buy a larger quantity to eat at home or share with relatives. If the price rises, the family may buy fewer mangoes or choose another fruit.
Economic lesson: Price affects the quantity people are willing and able to purchase, assuming their income, preferences, and other conditions do not change.
Example 3: Smartphones during a sale
A discount can bring more buyers into the market
A smartphone normally sells for ₹20,000. During a sale, its price falls to ₹17,000. Some shoppers who were waiting for a lower price may now decide to buy it. Others may consider upgrading sooner than planned.
Economic lesson: A lower price can increase quantity demanded. But if the sale also changes consumers' expectations, creates publicity, or coincides with a new model launch, those other factors may influence the observed change too.
Example 4: Car prices and buying decisions
Large purchases also involve budgets and alternatives
A family is considering a car but finds the original price beyond its budget. If the price falls or a discount reduces the amount payable, the family may decide to purchase. If the price rises, it may postpone the purchase or choose a less expensive model.
Economic lesson: Price changes can affect the quantity demanded, but a car's financing cost, income, fuel expenses, and competing models also matter in actual buying decisions.
Example 5: A limited shopping budget
The same budget can buy different quantities at different prices
Suppose you have ₹100 for notebooks. At ₹25 each, you can afford four notebooks. At ₹20 each, the same ₹100 could buy five. This shows how a lower price increases the quantity you can afford, although how many you actually want to buy depends on your needs.
₹25 per notebook
₹100 buys at most 4 notebooks.
₹20 per notebook
₹100 buys at most 5 notebooks.
6. Movement Along the Demand Curve vs. Shift in Demand
This distinction is important in economics examinations and in analysing real markets. A change in the product's own price generally causes a movement along the existing demand curve. A change in another factor that influences demand can shift the entire curve.
Movement along the curve
If the price of a product falls and consumers buy more of it, this is called an extension of demand. If its price rises and consumers buy less, it is called a contraction of demand.
Example
The price of a notebook falls from ₹25 to ₹20, and the consumer buys more notebooks.
Shift of the demand curve
Demand can increase or decrease when factors other than the product's own price change. The entire demand curve moves right or left.
Example
A consumer's income rises and they decide to buy more of a normal goods at every price.
| Situation | Type of change | What happens? |
|---|---|---|
| The product's own price falls | Extension of demand | Movement down the existing curve |
| The product's own price rises | Contraction of demand | Movement up the existing curve |
| Demand rises because of income or tastes | Increase in demand | Curve shifts to the right |
| Demand falls because preferences change | Decrease in demand | Curve shifts to the left |
A common mistake to avoid
Do not say that a lower price always shifts the demand curve to the right. A change in the good's own price causes movement along its demand curve. A shift occurs when another determinant of demand changes.
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7. Factors That Can Shift Demand
The law of demand studies the effect of a product's own price while other factors are held constant. In real markets, these other factors can change and shift the demand curve.
Consumer income
For many normal goods , higher income increases demand. For some inferior goods , demand can fall as income rises.
Prices of related goods
If the price of tea rises, some consumers may switch to coffee if they consider the two substitutes. If the price of printers rises, demand for compatible ink cartridges may also be affected because the products are complements.
Tastes and preferences
Advertising, trends, changing habits, or new information can make consumers more or less interested in a product.
Expectations
If consumers expect a price increase or shortage in the future, they may bring purchases forward. Expectations can also work in the opposite direction.
Number of buyers
If more consumers enter a market, total market demand may rise. If the number of buyers falls, market demand may decline.
8. Assumptions of the Law of Demand
The law is normally stated with the condition “other things remaining equal.” This helps isolate the relationship between price and quantity demanded.
Consumer income remains unchanged.
Consumer tastes and preferences remain unchanged.
Prices of related goods remain unchanged.
Consumer expectations about future prices and availability remain unchanged.
The number of buyers and other relevant market conditions remain unchanged.
9. Exceptions and Special Cases
The law of demand describes the usual pattern, but economists also study special cases where observed behaviour may differ. Some apparent exceptions occur because other factors change at the same time, while a few theoretical cases can produce an unusual relationship between price and quantity demanded.
Giffen goods
In a special theoretical case involving a strongly inferior staple goods and a tight household budget, a price increase can lead some consumers to buy more of that staple because the loss of purchasing power changes what they can afford. Genuine Giffen behaviour is unusual and requires specific conditions.
Prestige or status goods
Some buyers may associate a very high price with exclusivity or status. However, expensive luxury goods do not automatically violate the law of demand; an unusual relationship must be established rather than assumed.
Expectations of future price changes
If buyers expect a product to become more expensive soon, they may purchase more now even while its current price is rising. Expectations have changed, so this is not a clean test of the law with other factors held constant.
Essential goods
Consumers may have limited ability to reduce purchases of essential goods when prices rise. This often means demand is relatively inelastic, not necessarily that the law of demand is violated.
Important distinction
A product being expensive, essential, or fashionable is not by itself proof of an exception. Economists must distinguish a genuine change in the price–quantity relationship from changes in income, expectations, tastes, and other demand determinants.
10. Why the Law of Demand Matters
For consumers
Helps explain how prices affect shopping decisions and why consumers compare alternatives.
For businesses
Helps businesses think about pricing, promotions, customer response, and the possible effects of a price change.
For public policy
Helps economists analyse taxes, subsidies, price changes, and how consumers may respond to market policies.
Frequently Asked Questions
1. What is the law of demand?
The law of demand states that, other things remaining equal, quantity demanded generally increases when price falls and decreases when price rises.
2. Why does the demand curve slope downward?
A lower price can make a goods affordable to more buyers, encourage existing buyers to purchase more, and make the goods more attractive compared with substitutes. These effects help explain the usual inverse relationship between price and quantity demanded.
3. What is the difference between demand and quantity demanded?
Demand describes the relationship between different prices and the quantities consumers are willing and able to buy. Quantity demanded is the amount consumers want and can buy at one particular price during a given period.
4. What is the difference between a movement and a shift in demand?
A change in the good's own price causes movement along the existing demand curve. A change in income, tastes, expectations, or the price of a related goods can shift the entire demand curve.
5. Does the law of demand apply to every product?
It describes the usual relationship under stated assumptions, but unusual cases can occur. Some prestige goods , expectations of future price changes, or special market conditions may produce behaviour that differs from the usual pattern.
6. Does a price reduction always increase sales?
Not necessarily. The law describes the relationship between price and quantity demanded when other relevant factors are held constant. Actual sales also depend on availability, income, competition, preferences, product quality, and other conditions.
Key Takeaway
The law of demand describes the usual inverse relationship between a product's price and the quantity consumers demand, assuming other relevant factors remain unchanged. A demand schedule shows the relationship in a table, while a demand curve shows it graphically. Always distinguish movement along a curve caused by the product's own price from a shift caused by other changes in the market.
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