Law of Demand in Economics with Diagram


In the field of economics, few fundamental principles govern the way consumers interact with goods and services. Among these principles, the Law of Demand stands as a cornerstone, explaining the relationship between price and quantity demanded. This article delves deep into the Law of Demand, the factors influencing it, and its graphical representation through the demand curve. 

What is the Law of Demand?

The Law of Demand says that when the price of a good increases, the quantity demanded of that good decreases, ceteris paribus. In simpler terms, it means that when the price of a product rises, consumers always buy less of that product, assuming all other factors influencing demand remain constant. 

These factors include income, tastes, and expectations, among others. Understanding the Law of Demand is important for businesses, policymakers, and economists, as it shapes how consumers behave in response to price changes.

Definition of the Law of Demand by Different Authors

“Law of Demand states that people will buy more at lower prices and buy less at higher prices, if other things remain the same.

 Prof. Samuelson

The Law of Demand states that the amount demanded increases with a fall in price and diminishes when price increases.”

Prof. Marshall

“According to the law of demand, the quantity demanded varies inversely with price.”


“The greater the amount to be sold, the smaller must be the price”


“Usually a larger quantity of commodity will demanded at lower price that a higher price”


Demand Curve

Basically, the Law of Demand is represented by a downward-sloping curve known as the demand curve. This curve illustrates the inverse relationship between price and quantity demanded. As the price of a good increases, the curve slopes downward because consumers are more likely to seek cheaper alternatives or substitute other goods for the one with the higher price. In the other way, as the price decreases, consumers are more willing to purchase larger quantities of the product.

demand curve definepeida

The Slope of the Demand Curve

The slope of the demand curve is a crucial measure of how responsive quantity demand is to changes in price. It is calculated by dividing the change in quantity demanded by the change in price. The slope can be positive, negative, or zero, indicating different levels of responsiveness. 

A step negative slope suggests a significant decrease in quantity demanded with a slight increase in price, while a shallow negative slope indicates a relatively smaller decrease in quantity demanded with the same price increase. Zero slope means that the quantity demanded remains constant, regardless of price changes.

Factors That Affect Demand

While the Law of Demand provides a general understanding of consumer behavior, several factors can influence demand, leading to shifts in the demand curve. Some key factors include:

  1. Price of the Good: The most apparent factor affecting demand is the price of the product itself. As mentioned in the Law of Demand, higher prices typically result in reduced quantity demanded, and vice versa.
  2. Income: Changes in consumers’ income levels can significantly impact demand. When income rises, people tend to have more purchasing power, leading to an increase in demand for few goods and services. Conversely, a decrease in income may lead to decreased demand.
  3. Tastes and Preferences: Consumers’ tastes and preferences play a vital role in shaping their demand for specific products. Changing trends, fads, and cultural shifts can lead to fluctuations in demand for various goods and services.
  4. Expectations: Anticipated future changes in price, income, and other factors can influence present-day demand. For example, if consumers expect a future price increase for a product, they may rush to buy it now, leading to a temporary surge in demand.
  5. Substitutes and Complements: The availability and pricing of substitutes and complementary goods impact demand. Substitute goods are those that can replace each other in consumption, like tea and coffee, while complementary goods are consumed together, like smartphones and mobile data plans.


In the end, the Law of Demand is a pivotal idea in economics, explaining the inverse relationship between rate and quantity demanded. The demand curve visually represents this courting, with its downward slope indicating the effect of rate changes on consumer conduct. Understanding the factors that affect demand is essential for organizations and policymakers as they make informed choices about pricing strategies, advertising and marketing campaigns, and useful resource allocation.

So, by delving into the depths of the Law of Demand and its underlying ideas, we are hoping to equip our readers with a profound knowledge of this fundamental monetary idea. Armed with this knowledge, businesses can better navigate the market, customers can make informed alternatives, and economists can gain deeper insights into the intricacies of human conduct inside the face of converting economic situations.

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