Price Elasticity of Demand measures how responsive the quantity demanded of a product is to a change in its price.
It answers a practical question:
If the price of a food or agricultural product changes, how much will consumers change the quantity they buy?
This concept is important because the Law of Demand tells us the general direction of consumer response, while Price Elasticity of Demand tells us how strong that response is.
What Is Price Elasticity of Demand?
Suppose the price of apples rises by 10 percent.
If consumers reduce the quantity they purchase by 20 percent, Demand is relatively responsive.
Now suppose the price of a staple food rises by 10 percent but consumers reduce purchases by only 2 percent.
Demand is much less responsive.
Price Elasticity of Demand, commonly abbreviated as PED, measures this difference.
What Is the Formula?
The basic formula is:
Price Elasticity of Demand = Percentage Change in Quantity Demanded ÷ Percentage Change in Price
Suppose price rises by 10 percent and quantity demanded falls by 20 percent:
PED = −20% ÷ 10% = −2
Because price and quantity demanded usually move in opposite directions, PED is commonly negative.
Economists often use the absolute value when classifying Demand as elastic or inelastic.
What Is Elastic Demand?
Demand is generally considered elastic when the absolute value of PED is greater than 1.
This means quantity demanded changes proportionally more than price.
Products with many close substitutes may have more elastic Demand because consumers can switch to alternatives when prices increase.
What Is Inelastic Demand?
Demand is inelastic when the absolute PED is less than 1.
Quantity demanded changes proportionally less than price.
Some essential food products can have relatively inelastic Demand because households continue purchasing them even when prices change.
However, elasticity varies by product, location, income group and time period.
What Is Unit Elastic Demand?
Demand is unit elastic when the absolute elasticity equals 1.
A 10 percent increase in price accompanied by a 10 percent decline in quantity demanded represents unit elastic Demand.
What Determines Price Elasticity of Demand?
Important factors include:
availability of substitutes • necessity • share of household income • time • how narrowly the product is defined
A food product with many substitutes may have relatively elastic Demand.
A staple with few alternatives may have relatively inelastic Demand.
Consumers also have more opportunities to adjust behaviour over longer periods.
Price Elasticity and Total Revenue
Elasticity can affect Total Revenue.
If Demand is elastic, raising price may reduce sales by such a large percentage that Total Revenue falls.
If Demand is inelastic, a price increase may reduce sales only slightly and Total Revenue may rise.
This relationship is important for farmers, Agribusinesses and food companies.
Why Is Price Elasticity Important in Agriculture?
Price Elasticity helps explain consumer responses to:
food-price inflation • crop shortages • taxes • subsidies • trade shocks • market disruptions
It also matters for Food Security.
If an essential food has highly inelastic Demand, households may continue purchasing similar quantities despite higher prices, forcing them to devote more income to food.
Lower-income households can be particularly vulnerable.
Key Takeaways
- Price Elasticity of Demand measures responsiveness of quantity demanded to price changes.
- Its formula divides percentage change in quantity demanded by percentage change in price.
- Demand is elastic when the absolute elasticity is greater than 1.
- Demand is inelastic when the absolute elasticity is less than 1.
- Unit elastic Demand has an absolute elasticity of 1.
- Availability of substitutes, necessity, household budgets and time influence elasticity.
- Price Elasticity of Demand is closely related to Total Revenue.
- Elasticity helps explain how consumers respond to food-price changes.
- It has important implications for Food Security and Agricultural Policy.
Continue Exploring
Demand — Understand the broader concept of consumer Demand.
Law of Demand — Learn the general direction of consumer response.
Demand Curve — Explore Demand graphically.
Income Elasticity of Demand — Measure Demand response to income.
Cross-Price Elasticity — Understand Demand relationships among products.
Total Revenue — Explore the relationship between sales, price and revenue.
Food Security — Understand economic access to adequate food.
References and Further Reading
- USDA Economic Research Service. Food Demand Analysis. Provides authoritative definitions of own-price elasticity and explains elastic, inelastic and unit-elastic Demand.
USDA Food Demand Analysis - USDA Economic Research Service. Commodity and Food Elasticities — Glossary.
USDA Elasticities Glossary - USDA Economic Research Service. Commodity and Food Elasticities.
USDA Commodity and Food Elasticities Database - Zereyesus, Y. A., Xia, T., Nava, N. J., Li, X., & Cardell, L. International Income and Price Elasticity Estimates: An Update. USDA ERS, 2025.
USDA International Income and Price Elasticity Estimates - Massachusetts Institute of Technology. Principles of Microeconomics — Elasticity.
MIT Elasticity - OECD & FAO. OECD-FAO Agricultural Outlook 2026–2035.
OECD-FAO Agricultural Outlook 2026–2035