How does the law of demand help in setting prices?

In one line

The rule

The Law of Demand states that, all else being equal, as the price of a good or service decreases, the quantity demanded increases, and vice versa. This inverse relationship between price and quantity demanded is fundamental in economics.

Formula: Qd = f(P) (where Qd = quantity demanded, P = price)

Let's understand it simply

Imagine you are at the market to buy mangoes. If mangoes cost ₹200 per kg, you may buy only half a kilo. But if the price drops to ₹80 per kg, you might buy 2 kg. This is because you feel you are getting more value for your money. Sellers know this. If they set the price too high, only a few people will buy. If they set it too low, many people will buy, but the seller may not earn enough. So, sellers use the law of demand to find a price where enough people buy, and they still make a profit.

How it works

1. Sellers check how much people want to buy at different prices (demand).
2. They notice that when they lower the price, more people buy the product.
3. If they raise the price, fewer people buy.
4. Sellers use this information to set a price that attracts enough buyers and gives them a good income.
5. Sometimes, sellers test prices and watch how demand changes, then adjust the price again.
6. During sales or festivals, sellers may lower prices to increase demand and sell more goods quickly.

The story behind it

The law of demand was noticed by early economists in the 18th and 19th centuries, like Alfred Marshall, who wrote about it in his book "Principles of Economics" in 1890. They wanted to understand why prices go up or down in markets. The law of demand helped explain how buyers and sellers interact, and why prices change when there is more or less demand for a product. Marshall used simple graphs to show this relationship, which are still used in textbooks today.

Where you see it in real life

• Vegetable market: When onions become expensive in the monsoon, people buy less, or switch to potatoes.
• Mobile phones: When a new phone launches at a high price, only a few buy. When the price drops after a few months, more people buy it.
• Movie tickets: On weekdays, cinema halls lower ticket prices to attract more viewers, filling up empty seats.
• Online sales: During Diwali, websites like Amazon or Flipkart offer discounts. The lower price increases demand, and more people buy.
• Bus fares: If a private bus raises its fare, some passengers may choose a cheaper government bus instead.
• Ice cream in summer: Sellers may keep prices steady, knowing demand is high, but may offer discounts in winter to boost sales.

Why it matters

• Helps businesses set the right price: If the price is too high, they lose customers. If too low, they lose profit.
• Guides government policy: When setting prices for essentials (like LPG or rice), the government checks how demand will change.
• Predicts sales: Shops can plan how much stock to keep, based on expected demand at different prices.
• Used in exams and higher studies: Understanding this law is key for economics, business studies, and competitive exams.

Worked example

Let's say a shop sells apples.

Given:  Price per kg drops from ₹100 to ₹80
Step 1: At ₹100 per kg, quantity demanded = 50 kg
Step 2: At ₹80 per kg, quantity demanded = 70 kg
Step 3: Law of demand says: as price decreases, quantity demanded increases
Step 4: The shopkeeper sees more apples are sold at ₹80, so may keep the price lower to sell more

Common mistakes

• Thinking demand always increases, no matter the price: In reality, higher prices usually reduce demand.
• Forgetting 'all else being equal': The law works only if other things (like income, taste, or prices of other goods) do not change.
• Confusing demand with quantity demanded: 'Demand' means the whole relationship; 'quantity demanded' is the amount at a specific price.
• Believing the law works for every product: Some goods (like medicines or salt) do not follow this law strictly, because people need them no matter the price.

Remember it

"Lower price, higher demand; higher price, lower demand."