Price Elasticity of Demand (PED)

Price Elasticity of Demand (PED) is a fundamental concept in microeconomics that quantifies the sensitivity of quantity demanded to changes in price. It helps us understand consumer behaviour and predict how sales will react to price adjustments. The formula for PED is:

PED = (% Change in Quantity Demanded) / (% Change in Price)

• Percentage Change in Quantity Demanded = [(New Quantity - Old Quantity) / Old Quantity] * 100
• Percentage Change in Price = [(New Price - Old Price) / Old Price] * 100

It's important to note that PED is typically a negative value because of the law of demand (price and quantity demanded move in opposite directions). However, for analytical purposes, economists usually consider the absolute value of PED. A higher absolute value indicates greater responsiveness, while a lower absolute value indicates less responsiveness. Understanding PED is vital for firms in setting optimal prices and for governments in assessing the impact of taxes on consumer behaviour and revenue.

The numerical value of PED provides crucial insights into the nature of demand:

• PED > 1 (Elastic Demand): This means that a given percentage change in price leads to a proportionally larger percentage change in quantity demanded. For example, if PED = 2, a 10% price increase leads to a 20% decrease in quantity demanded. Goods with elastic demand often have many substitutes or are luxury items.

• PED < 1 (Inelastic Demand): This indicates that a given percentage change in price leads to a proportionally smaller percentage change in quantity demanded. For example, if PED = 0.5, a 10% price increase leads to only a 5% decrease in quantity demanded. Necessities or goods with few substitutes tend to have inelastic demand.

• PED = 1 (Unitary Elastic Demand): Here, the percentage change in quantity demanded is exactly equal to the percentage change in price. A 10% price increase leads to a 10% decrease in quantity demanded. Total revenue remains unchanged with price adjustments.

• PED = 0 (Perfectly Inelastic Demand): Quantity demanded does not change at all, regardless of price changes. This is rare in reality but can apply to life-saving drugs with no substitutes. The demand curve is vertical.

• PED = ∞ (Perfectly Elastic Demand): Consumers will demand an infinite quantity at a specific price, but none at a slightly higher price. This is characteristic of perfect competition where firms are price takers. The demand curve is horizontal.

Several factors influence the PED for a good or service:

• Availability of Substitutes: The more substitutes available for a good, the more elastic its demand will be. If the price of one good rises, consumers can easily switch to an alternative. For example, branded coffee vs. coffee in general.

• Necessity vs. Luxury: Necessities (e.g., basic food, essential medicine) tend to have inelastic demand because consumers need them regardless of price. Luxury goods (e.g., designer clothes, expensive holidays) tend to have elastic demand as consumers can easily forgo them if prices rise.

• Proportion of Income Spent on the Good: Goods that represent a small fraction of a consumer's income (e.g., salt, matches) tend to have inelastic demand. A price change has little impact on their overall budget. Goods that represent a large proportion of income (e.g., cars, houses) tend to have more elastic demand.

• Time Horizon: Demand tends to be more elastic in the long run than in the short run. In the short run, consumers may not have time to find substitutes or adjust their consumption habits. Over a longer period, they can find alternatives, change their behaviour, or adapt to new prices.

• Addictiveness/Habit-forming Goods: Goods like cigarettes or certain drugs often have highly inelastic demand due to addiction, making consumers less responsive to price changes.