1.2.3.3 Stable versus unstable equilibrium

In economics, equilibrium refers to a state in the market where the quantity demanded by consumers is equal to the quantity supplied by producers, resulting in a stable market outcome. However, not all equilibria are the same, and they can be classified into two main categories: stable equilibrium and unstable equilibrium. Let’s explore the differences between these two types of equilibrium:

1. Stable Equilibrium: Stable equilibrium occurs when the market tends to return to the equilibrium position after experiencing a small disturbance or shock. In other words, if the market is at a stable equilibrium, any deviations from that equilibrium will be self-correcting, and the market will eventually move back to the original equilibrium.

Graphically, in a stable equilibrium, the demand and supply curves intersect at a point where the quantity demanded equals the quantity supplied. If the market price and quantity deviate slightly from this equilibrium point, market forces such as changes in consumer behavior and producer responses will work to bring the market back to the original equilibrium.

2. Unstable Equilibrium: Unstable equilibrium, on the other hand, occurs when the market tends to move further away from the equilibrium position after experiencing a small disturbance or shock. In this case, any deviations from the equilibrium will amplify, causing the market to move away from the original equilibrium.

Graphically, in an unstable equilibrium, the demand and supply curves intersect at a point where the quantity demanded equals the quantity supplied. However, if the market price and quantity deviate slightly from this equilibrium point, market forces will reinforce the deviation and push the market further away from the original equilibrium.

Illustration: Imagine a market with a stable equilibrium at a price of sh10 and a quantity of 100 units. If the price temporarily increases to sh12, consumers may reduce their quantity demanded, and producers may increase their quantity supplied in response to the higher price. As a result, the market will move back toward the original equilibrium of sh10 and 100 units.

In contrast, in an unstable equilibrium scenario, a temporary increase in price to sh12 might lead to further reductions in quantity demanded and increased quantity supplied, causing the market to move even farther away from the original equilibrium.