The phrase "supply and demand" was first used by James Denham-Steuart in his Inquiry into the Principles of Political Economy, published in 1767. Adam Smith used the phrase in his 1776 book The Wealth of Nations, and David Ricardo titled one chapter of his 1817 work Principles of Political Economy and Taxation "On the Influence of Demand and Supply on Price"

The model was further developed and popularized by Alfred Marshall in the 1890 textbook Principles of Economics.Along with Léon Walras, Marshall looked at the equilibrium point where the two curves crossed.

Supply and Demand Model

In economics, supply and demand describe market relations between prospective sellers and buyers of a good.

The supply and demand model determines price and quantity sold in the market. The model is fundamental in microeconomic analysis of buyers and sellers and of their interactions in a market. It is also used as a point of departure for other economic models and theories. The model predicts that in a competitive market, price will function to equalize the quantity demanded by consumers and the quantity supplied by producers, resulting in an economic equilibrium of price and quantity.

The Laws of Supply v/s The Laws of Demand

The law of supply states that quantity supplied is related to price. It is often depicted as directly proportional to price: the higher the price of the product, the more the producer will supply, ceteris paribus.

The law of demand is normally depicted as an inverse relation of quantity demanded and price: the higher the price of the product, the less the consumer will demand.

The laws of supply and demand state that the equilibrium market price and quantity of a commodity is at the intersection of consumer demand and producer supply.

Here, quantity supplied equals quantity demanded that is, equilibrium. Equilibrium implies that price and quantity will remain there if it begins there.

If the price for a good is below equilibrium, consumers demand more of the good than producers are prepared to supply. This defines a shortage of the good. A shortage results in the price being bid up. Producers will increase the price until it reaches equilibrium.

If the price for a good is above equilibrium, there is a surplus of the good. Producers are motivated to eliminate the surplus by lowering the price. The price falls until it reaches equilibrium.