Equilibrium, Excess Demand, Excess Supply
Categories: Freshers Study Economics Intermediate class NCERT
Equilibrium, Excess Demand, Excess Supply
An equilibrium is defined as a situation where the plans of all consumers and firms in the market match and the market clears. In equilibrium, the aggregate quantity that all firms wish to sell equals the quantity that all the consumers in the market wish to buy; in other words, market supply equals market demand. The price at which equilibrium is reached is called equilibrium price and the quantity bought and sold at this price is called equilibrium quantity. Therefore, (p * , q* ) is an equilibrium if q D (p ∗ ) = q S (p ∗ ) where p ∗ denotes the equilibrium price and q D (p ∗ ) and q S (p ∗ denote the market demand and market supply of the commodity respectively at price p If at a price, market supply is greater than market demand, we say that there is an excess supply in the market at that price and if market demand exceeds market supply at a price, it is said that excess demand exists in the market at that price. Therefore, equilibrium in a perfectly competitive market can be defined alternatively as zero excess demand-zero excess supply situation. Whenever market supply is not equal to market demand, and hence the market is not in equilibrium, there will be a tendency for the price to change. In the next two sections, we will try to understand what drives this change.
Out-of-equilibrium Behaviour
From the time of Adam Smith (1723-1790), it has been maintained that in a perfectly competitive market an ‘Invisible Hand’ is at play which changes price whenever there is imbalance in the market. Our intuition also tells us that this ‘Invisible Hand’ should raise the prices in case of ‘excess demand’ and lower the prices in case of ‘excess supply’. Throughout our analysis we shall maintain that the ‘Invisible Hand’ plays this very important role. Moreover, we shall take it that the ‘Invisible Hand’ by following this process is able to reach the equilibrium. This assumption will be taken to hold in all that we discuss in the text.