What it means
The idea is a ratio of percentage changes rather than absolute amounts, which makes it comparable across products of very different sizes. Because quantity normally falls when price rises, price elasticity of demand is usually a negative number, and most people quote it as an absolute value out of habit.
The dividing line sits at 1. Above 1 in absolute terms demand is elastic and a price rise reduces total revenue, below 1 demand is inelastic and a price rise increases total revenue, and exactly 1 means revenue is unchanged.
What makes demand elastic is mostly the availability of substitutes and the share of a customer's budget the item takes. Branded soft drinks on a supermarket shelf face many close substitutes and are elastic, while insulin, cigarettes and the only ferry to an island are inelastic for obvious reasons.
Businesses use elasticity to set prices, plan promotions and forecast the volume effect of a change before making it. A retailer that estimates elasticity of -0.6 on a staple product knows a 5% price rise loses only about 3% of units and therefore adds revenue, while the same rise on an elastic product would go the other way.
Elasticity is not limited to price. Income elasticity shows how demand responds to customers getting richer or poorer, and cross-price elasticity shows how one product's demand responds to a rival's or a companion product's price, which is how firms identify substitutes and complements from data rather than intuition.
In practice
Real-world examples.
Example
A cinema chain raises adult evening tickets from $14 to $15 and loses 2% of admissions. Elasticity of about -0.28 means demand is inelastic, revenue rises, and the chain repeats the increase the following year.
Example
An online clothing retailer runs a 20% discount and sees units jump 60%. That implies elasticity around -3, which is highly elastic, but the finance team notes the discount also cut gross margin per unit, so the promotion grew revenue while shrinking profit.
Example
A regional bus operator increases fares 8% and sees ridership drop 12% as commuters switch to driving. Elasticity of -1.5 shows a viable substitute exists, and the operator responds by holding fares and improving frequency instead.
Formula
Calculation
Price elasticity of demand = Percentage change in quantity demanded / Percentage change in price.
A speciality coffee roaster sells 20,000 bags a month at $50 and raises the price to $55.
Percentage change in price = ($55 - $50) / $50 = 10%
Volume falls from 20,000 bags to 17,000 bags
Percentage change in quantity = (17,000 - 20,000) / 20,000 = -15%
Elasticity = -15% / 10% = -1.5
Demand is elastic, so check what happened to revenue:
Revenue before = $50 x 20,000 = $1,000,000
Revenue after = $55 x 17,000 = $935,000
Revenue change = -$65,000
The price rise cost $65,000 of monthly revenue. If the roaster's gross margin per bag were also known, the decision could still be defensible, since 3,000 fewer bags means lower coffee, packaging and shipping costs, but on revenue alone the elastic response made the increase a losing move.Case study
Seen in the real world.
What follows is an illustrative, fictional example. Marlowe Garden Tools sold two product lines through the same garden centres: a $25 hand trowel and a $340 professional hedge trimmer. Under margin pressure, the board approved an across-the-board 8% price rise on both lines.
Six months of sales data showed two very different outcomes. Trowel volumes fell only 2%, an elasticity of roughly -0.25, because $2 hardly registers on an impulse purchase, while trimmer volumes fell 14%, an elasticity of about -1.75, because trade buyers compared prices carefully and two rivals held theirs.
Marlowe reversed the trimmer increase, kept the trowel increase, and adopted a simple rule for the illustrative benefit of future planning: measure elasticity by line before pricing, because one company can easily contain both an inelastic impulse product and an elastic considered purchase.
Watch out
Common mistakes.
- Applying one elasticity figure across a whole product range. Elasticity varies by product, customer segment, season and channel, so a company-wide number hides the differences that matter most.
- Reading elasticity as a permanent property. It changes when new substitutes appear, when incomes shift and when customers have had time to adjust, so short-run and long-run elasticity often differ substantially.
- Judging a price change on revenue alone. Lower volumes cut variable costs too, so an elastic response can still improve profit if the margin per unit rises enough.
Questions
People also ask.
Why is price elasticity usually negative?
Because price and quantity normally move in opposite directions, and the minus sign simply records that relationship rather than indicating anything unusual.
How do I estimate elasticity for my own products?
Use past price changes and promotions as natural experiments, or run controlled tests in a subset of stores or regions, then compare percentage volume change with percentage price change.
What does an elasticity of exactly -1 mean?
Revenue stays flat when you change price, because the percentage volume loss exactly offsets the percentage price gain.
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