What it means
Elasticity converts a vague instinct that customers are price sensitive into a number you can plan with. Instead of arguing about whether a 10% rise is safe, you can state that a 10% rise historically costs about 15% of unit volume and work out what that does to profit.
The sign is almost always negative because price and quantity move in opposite directions, so most people quote the figure without the minus sign and simply describe demand as elastic or inelastic. Elastic demand, above 1 in absolute size, means volume reacts more than proportionately to price; inelastic demand, below 1, means volume barely moves.
What drives elasticity is mostly the availability of substitutes and the share of the customer's budget the item takes up. Petrol, prescription medicines and utility water are inelastic because there is nowhere else to go, whereas one brand of biscuit sitting next to five others on a shelf is highly elastic.
Elasticity is not fixed. It changes with time horizon, because customers need months to find alternatives, and it changes with the size of the move, since a 3% rise may pass unnoticed while a 30% rise triggers a search for a substitute.
The practical trap is measuring it badly. Comparing last year's price and volume with this year's confuses the effect of price with everything else that changed, so credible estimates come from controlled tests, regional trials or careful modelling that holds other factors steady.
In practice
Real-world examples
Example 1
A city transport authority raises single fares by 8% and finds ridership drops only 2%, an elasticity of about -0.25. Because commuters have few alternatives at rush hour, the increase raises revenue and the authority uses the surplus to fund extra evening services.
Example 2
A snack brand tests a 15% price rise in two supermarket regions and loses 27% of unit sales, an elasticity near -1.8. The category has many close substitutes on the same shelf, so the brand reverses the rise and looks for cost savings instead.
Example 3
A business software vendor increases its annual subscription by 6% and sees churn rise by less than 1 percentage point. The switching cost of migrating data makes demand highly inelastic in the short run, though the vendor knows repeated increases would eventually push customers to evaluate rivals.
Think of it
Think of price elasticity like stretching a rubber band. An elastic product stretches easily and snaps back with a big reaction when pulled. An inelastic product is like a thick leather strap that barely moves when you pull it.
Formula
Calculation
Price Elasticity of Demand = % change in quantity demanded / % change in price
A specialty coffee roaster sells a 1kg bag of beans at $20 and moves 10,000 bags a month. It raises the price to $22 and, after three months, monthly volume has settled at 8,500 bags.
Percentage change in price = ($22 - $20) / $20 = 0.10, or a 10% rise
Percentage change in quantity = (8,500 - 10,000) / 10,000 = -0.15, or a 15% fall
Elasticity = -15% / 10% = -1.5
Demand is elastic, so total revenue should fall, and it does. Revenue before the rise was 10,000 x $20 = $200,000 a month. Revenue after is 8,500 x $22 = $187,000, a drop of $13,000 or 6.5%.
Revenue is not the whole story though. If each bag costs $12 to produce and pack, contribution before was 10,000 x ($20 - $12) = $80,000 and after is 8,500 x ($22 - $12) = $85,000, so profit actually improves by $5,000 even though revenue falls. Elastic demand means a price rise shrinks revenue, but whether it shrinks profit depends on the margin.Case study
Seen in the real world
This is an illustrative, fictional example rather than a real company. Fernvale Gardens, an invented chain of eleven garden centres, had raised prices across the board by 5% each spring for years without measuring what happened. A new commercial manager split the estate into two matched groups for a season and ran different price changes in each.
The test showed that elasticity varied enormously by category. Seasonal bedding plants came out around -2.1, since shoppers compared them with supermarket offers, while potting compost, tools and garden furniture all landed between -0.3 and -0.6 because customers bought them on convenience during a single visit.
Fernvale rebuilt its pricing on that evidence, holding bedding plants flat as a footfall driver and raising the inelastic categories by 9%. In this illustrative outcome, transaction counts were unchanged, average basket value rose by about 6%, and gross profit grew by a little over $900,000 across the chain, without a single across-the-board increase.
Watch out
Common mistakes
- Quoting elasticity as a positive number without saying so. The true value is negative, and mixing signed and unsigned figures in the same discussion leads to people reading an elastic product as inelastic.
- Assuming one elasticity applies to the whole business. Elasticity differs by product, channel, customer segment and season, so a single company-wide number hides the very variation that makes the analysis useful.
- Optimising revenue instead of profit. An elastic product can still be worth repricing upwards if the margin per unit rises enough to offset lost volume, which is why contribution must be modelled alongside revenue.
Questions
People also ask
What counts as elastic or inelastic?
Ignoring the sign, above 1 is elastic and means quantity reacts more than price, below 1 is inelastic, and exactly 1 is unit elastic where revenue stays unchanged.
Why do economists use the midpoint formula?
Using the average of the starting and ending values as the base gives the same elasticity whether the price rises or falls, which avoids the awkward asymmetry of simple percentage change.
Can elasticity be measured without running experiments?
You can estimate it from historical data or industry norms, but promotions, competitor moves and seasonality contaminate the picture, so a controlled regional test remains far more reliable.