Why does the price of insulin stay high even when pharmaceutical companies raise it? Why do airlines constantly change ticket prices? Why do luxury brand handbags sometimes cost more than the market expects and still sell out?

The answer to all of these questions involves the same economic concept: price elasticity. It is one of the most practically useful ideas in economics, and understanding it explains pricing decisions that otherwise seem arbitrary or counterintuitive.

The Core Concept: How Sensitive Is Demand to Price?

Price elasticity of demand (PED) measures the relationship between a change in price and the resulting change in quantity demanded. Specifically, it tells you: if a product's price goes up by 1%, how much does demand (quantity purchased) change?

The formula is:

PED = % change in quantity demanded / % change in price

Because higher prices almost always reduce demand, the result is typically negative. Economists often use the absolute value to simplify discussion (so a PED of -0.5 is often discussed as simply "0.5").

Elastic vs. Inelastic

The critical threshold is 1:

• Elastic demand (|PED| > 1): A 1% price increase causes a greater than 1% drop in demand. Price changes cause proportionally larger changes in quantity.
• Inelastic demand (|PED| < 1): A 1% price increase causes a less than 1% drop in demand. Price changes barely affect how much people buy.
• Unit elastic (|PED| = 1): Price and quantity change in exact proportion.
• Perfectly inelastic (|PED| = 0): Price has no effect on demand whatsoever. Theoretical, but insulin for type 1 diabetics approaches this.
• Perfectly elastic (|PED| = infinity): Even a tiny price increase destroys all demand. Also theoretical -- approximately true for commodities on public exchanges where all sellers offer identical products.

| Elasticity Type | |PED| Value | What Happens When Price Rises 10% | |----------------|-----------|-----------------------------------| | Perfectly inelastic | 0 | No change in demand | | Inelastic | 0 to 1 | Demand falls less than 10% | | Unit elastic | 1 | Demand falls exactly 10% | | Elastic | 1 to infinity | Demand falls more than 10% | | Perfectly elastic | Infinity | Demand falls to zero |

What Determines Whether Demand Is Elastic or Inelastic?

Several factors systematically affect elasticity. Understanding them lets you estimate elasticity before collecting data.

Availability of Substitutes

This is the primary driver. If close substitutes exist, a price increase sends buyers to alternatives, making demand elastic. If no substitutes exist, buyers must pay whatever the price is.

Insulin for type 1 diabetes: Extremely inelastic. Patients will go into life-threatening ketoacidosis without it. There is no substitute.

Brand-name cola: Moderately elastic. Pepsi, store brands, and water are all substitutes. A large price increase on Coca-Cola causes many consumers to switch.

Gasoline broadly: Inelastic (-0.2 to -0.4). Over the medium term, consumers can switch to electric vehicles, public transit, or move closer to work -- making long-run elasticity higher than short-run elasticity.

Whether the Good Is a Necessity or a Luxury

Necessities (food, housing, utilities, medicine) tend to be inelastic. Consumers buy them regardless of price. Luxuries (restaurant meals, jewelry, vacations) are elastic -- consumers can delay or forgo them.

However, the distinction is not always intuitive. Tobacco and alcohol are considered necessities by dependent users, making them inelastic despite being widely considered luxuries. This is why tobacco taxes are a reliable revenue source for governments -- the tax reduces consumption somewhat but not proportionally.

Time Horizon

Demand almost always becomes more elastic over time. In the short run, consumers cannot easily change habits or find alternatives. In the long run, they can.

When gas prices spiked in 2022, short-term demand was relatively inelastic -- people had to get to work. Over the following 18 months, sales of fuel-efficient vehicles accelerated, and electric vehicle adoption increased. The long-run response is larger than the short-run response.

Share of Income

Goods that represent a large share of consumer budgets tend to attract more price sensitivity. A 10% increase in rent prices is agonizing and behavior-changing for most renters. A 10% increase in the price of table salt barely registers -- it is too small a fraction of any household's budget to think about carefully.

Definition of the Market

This is a subtlety that matters enormously in practice. Broadly defined markets are more inelastic than narrowly defined markets.

"Food" is highly inelastic -- people do not stop eating. "Restaurant meals at full-service sit-down establishments" is moderately elastic -- people can cook at home or eat at fast food instead. "Upscale Italian restaurants in downtown Chicago" is highly elastic -- there are many substitutes at every level of abstraction.

Real-World Elasticity Estimates

Academic economists and industry researchers have measured elasticity for many categories:

Product/Service	Estimated PED	Type
Gasoline (short-run US)	-0.2 to -0.4	Inelastic
Cigarettes (general)	-0.3 to -0.5	Inelastic
Prescription drugs (chronic)	-0.1 to -0.3	Highly inelastic
Food (all categories)	-0.1 to -0.2	Highly inelastic
Restaurant meals	-0.7 to -1.1	Slightly elastic
Economy air travel	-0.8 to -1.5	Elastic
Luxury goods (broad)	-1.2 to -2.0	Elastic
Specific brand within category	-3.0 to -5.0+	Highly elastic

Note: Elasticity varies by country, income level, time period, and market structure. These figures are approximations from the academic literature.

Price Elasticity and Total Revenue

One of the most practically important implications of elasticity is its relationship to total revenue (price x quantity).

If demand is inelastic: Raising prices increases total revenue, because the percentage drop in quantity is smaller than the percentage increase in price.

Example: A drug with PED = -0.2 is priced at $100. Raise the price to $120 (20% increase). Demand falls by only 4% (20% x 0.2). If original demand was 1,000 units, new demand is 960 units. Original revenue: $100,000. New revenue: $115,200. Revenue increased despite lower volume.

If demand is elastic: Raising prices decreases total revenue, because the percentage drop in quantity exceeds the percentage increase in price.

Example: A restaurant dish with PED = -1.5 is priced at $20. Raise the price to $22 (10% increase). Demand falls by 15% (10% x 1.5). Original orders: 500/week. New orders: 425/week. Original revenue: $10,000/week. New revenue: $9,350/week. Revenue fell.

If demand is unit elastic: Total revenue is unchanged by price movements. This is a mathematical curiosity -- raising prices neither helps nor hurts revenue.

"The strategic implication is clear: for inelastic products, price increases are largely free money. For elastic products, they require careful balancing against volume loss. This asymmetry drives almost every major pricing decision in business."

Cross-Price Elasticity: Complements and Substitutes

Cross-price elasticity of demand (CPED) measures how demand for product A changes when the price of product B changes:

CPED = % change in quantity of A / % change in price of B

Substitutes: Positive CPED

When the price of one good rises and demand for another good increases, they are substitutes. Examples:

• Butter and margarine
• Uber and Lyft
• Android and iOS devices
• Netflix and Hulu

A positive cross-price elasticity is evidence of competitive substitutability. The higher the number, the closer the substitutes -- meaning they compete more directly.

This matters enormously for antitrust analysis. Courts and regulators use cross-price elasticity to define markets. If raising the price of Pepsi causes consumers to buy significantly more Coke, the two products are in the same market.

Complements: Negative CPED

When the price of one good rises and demand for another good falls, they are complements -- used together. Examples:

• Printers and ink cartridges
• Coffee makers and coffee pods
• Streaming services and internet subscriptions
• Gaming consoles and game titles

A negative cross-price elasticity is the mathematical signature of a complementary relationship. This is why printer manufacturers historically priced printers cheaply and charged high margins on cartridges -- low printer prices increase total printer demand, which increases cartridge demand. The profit extraction happens at the complement stage.

Income Elasticity: How Demand Changes with Wealth

Income elasticity of demand measures how demand changes when consumer incomes change:

YED = % change in quantity demanded / % change in income

Normal Goods (Positive YED)

Most goods have positive income elasticity -- as people get richer, they buy more. Examples include restaurant meals, travel, and consumer electronics.

Luxury goods have high positive income elasticity (YED > 1). As incomes rise 10%, demand for luxury goods rises more than 10%. This is why the luxury sector is sensitive to economic cycles and why luxury brand penetration rises sharply with national GDP.

Inferior Goods (Negative YED)

Inferior goods are goods for which demand falls as income rises. As people get richer, they buy less of these things. Examples:

• Bus travel (substituted with cars as income rises)
• Budget store-brand groceries (substituted with name brands)
• Instant ramen (substituted with fresh food)
• Fast food (partially -- wealthier consumers eat at sit-down restaurants more often)

Understanding income elasticity matters for strategic planning. A business selling inferior goods grows during recessions and contracts during economic expansion. A luxury brand does the opposite. Planning accordingly requires knowing where on the income elasticity spectrum your products sit.

How Businesses Use Price Elasticity

Dynamic Pricing

Airlines are the canonical example of dynamic pricing -- adjusting prices continuously based on real-time signals about demand. An unsold seat on a departing flight has zero value; filling it at any positive price is better than flying empty. Airlines therefore drop prices as departure approaches if demand is below expectations, and raise them if demand is high.

Hotels, ride-sharing platforms, and concert ticketing use similar algorithms. The goal is to price each unit as close to the customer's maximum willingness to pay as possible -- capturing consumer surplus that flat pricing leaves on the table.

Price Discrimination

Price discrimination involves charging different prices to different customer segments based on their willingness to pay (which reflects their individual elasticity).

Examples:

• Student and senior discounts: Students and seniors often have higher price elasticity (limited income) -- charging them less increases total revenue without reducing prices for full-paying customers
• Geographic pricing: Software is priced differently in India versus the United States, reflecting different income levels and competitive alternatives
• Business vs. economy airline seats: The same seat position on the plane, priced dramatically differently. Business travelers (often on expense accounts, with less price sensitivity) pay for priority boarding, extra legroom, and status -- all proxies for inelastic demand
• Subscription tiers: Offering free, basic, and premium tiers allows customers to self-sort by willingness to pay

Promotional Pricing and Loss Leaders

Retailers use inelastic anchor products to build store traffic, then make margin on elastic products where they have pricing power. Supermarkets often sell milk and bread at thin margins (customers know the price and are sensitive to it) while making margin on prepared foods and specialty items where customers are less price-savvy.

Loss leaders -- products priced below cost to attract customers -- work precisely because the complementary or subsequent purchases are profitable.

Value-Based Pricing

For business-to-business products, elasticity analysis supports value-based pricing -- pricing based on the economic value delivered to customers rather than cost-plus formulas.

A software product that saves a company $500,000 per year can be priced at $50,000-$100,000 and still deliver massive value. The pricing is anchored to value delivered (which reduces the customer's effective elasticity, because the alternative -- not buying -- is more costly than a price increase).

Common Misunderstandings About Elasticity

"Luxury goods are always elastic": This conflates luxury with elasticity. True luxury goods -- Hermes bags, Rolex watches, Formula 1 racing tickets -- can exhibit Veblen behavior, where higher prices actually increase desirability by signaling exclusivity. A Rolex at half-price might actually sell fewer units because the status signal is compromised. This is a genuine exception to the typical demand curve.

"Inelastic means customers are captive forever": Inelasticity is typically a short-run or medium-run phenomenon. Over long periods, consumers adapt, new substitutes enter the market, and regulatory action may change the pricing environment. Pharmaceutical companies that exploit inelastic demand for patent-protected drugs face generic competition when patents expire.

"Price elasticity is fixed": Elasticity changes with income levels, competitor activity, consumer awareness, and time. A product's elasticity in a recession differs from its elasticity in an expansion. Measuring it once and assuming permanence is a common mistake.

Conclusion

Price elasticity is one of those economic concepts that sounds abstract until you see it in your own purchasing behavior. The reason you do not price-shop much on prescription medications but spend an hour comparing airline tickets is elasticity. The reason pharmaceutical companies, utilities, and addictive product companies can raise prices repeatedly without proportional demand loss is elasticity. The reason airlines and hotels change prices minute by minute is an attempt to price at each customer's individual elasticity.

For anyone in business, pricing is one of the most direct levers on profitability -- and elasticity is the theory that makes pricing decisions systematic rather than intuitive. Understanding whether your product is elastic or inelastic, and why, is foundational to knowing how to price it, how to segment your customer base, and how to respond to competitive pressure.

The formula is simple. The implications run through almost every major business decision.

Frequently Asked Questions

What is price elasticity of demand?

Price elasticity of demand (PED) measures how much the quantity demanded of a product changes in response to a price change. It is calculated as the percentage change in quantity demanded divided by the percentage change in price. An elasticity greater than 1 (in absolute value) means demand is elastic -- a price increase causes a proportionally larger drop in demand. Less than 1 means demand is inelastic -- quantity demanded is relatively insensitive to price changes.

What are examples of inelastic demand?

Gasoline, prescription medications, cigarettes, and utilities are classic examples of inelastic demand. Consumers buy similar quantities even when prices rise because these products are necessities with few substitutes. Studies have estimated gasoline's price elasticity at around -0.2 to -0.4, meaning a 10% price increase only reduces demand by 2-4%. Insulin has near-zero elasticity for diabetics who have no substitute.

What are examples of elastic demand?

Luxury goods, restaurant meals, airline tickets (economy class), and brand-name consumer electronics tend to have elastic demand. When prices rise significantly, consumers substitute with alternatives, delay purchases, or go without. Air travel price elasticity is typically estimated between -0.8 and -1.5, meaning demand is roughly proportional to price changes. Specific brand products within a category (one brand of ketchup vs another) often have high elasticity because substitutes are readily available.

What is cross-price elasticity of demand?

Cross-price elasticity measures how demand for one product changes when the price of a different product changes. Positive cross-price elasticity indicates substitutes: if the price of butter rises and demand for margarine increases, they are substitutes. Negative cross-price elasticity indicates complements: if the price of printers falls and demand for ink cartridges rises, they are complements. This helps businesses understand competitive dynamics and pricing strategy.

How do businesses use price elasticity?

Businesses use elasticity estimates to set optimal prices and predict the revenue impact of price changes. For inelastic products, raising prices increases total revenue because the drop in demand is smaller than the price increase. For elastic products, lowering prices can increase total revenue by attracting proportionally more buyers. Airlines and hotels use dynamic pricing algorithms that continually adjust prices based on real-time elasticity signals. Retailers use A/B pricing tests to directly measure elasticity for specific products.